Z-  P.  METCALI 


LIBRARY     OF 


1885- IQ56 


/ 


c 


4. 


ENTOMOLOGY 


FOLSOM 


ENTOMOLOGY 


WITH  SPECIAL  REFERENCE  TO 


ITS  ECOLOGICAL  ASPECTS 


BY 


JUSTUS  WATSON  FOLSOM,  Sc.D.   (Harvard) 

ASSISTANT   PROFESSOR   OF   ENTOMOLOGY   AT  THE    UNIVERSITY   OF   ILLINOIS 


THIRD  REVISED  EDITION 
WITH  FIVE  PLATES  AND  308  TEXT-FIGURES 


PHILADELPHIA 

P.    BLAKISTON'S   SON   &   CO. 

1012   WALNUT   STREET 


Copyright,  1922,  by  P.  Blakiston's  Son  &  Co. 


P  R  I  NTED  IN  U.  S 
THE  MAPLE  PRESS 


PREFACE 


This  book  gives  a  comprehensive  and  concise  account  of  insects. 
Though  planned  primarily  for  the  student,  it  is  intended  also  for  the 
general  reader. 

The  book  was  written  in  an  effort  to  meet  the  growing  demand  for  a 
biological  treatment  of  entomology. 

The  existence  of  several  excellent  works  on  the  classification  of 
insects  (notably  Comstock's  Manual,  Kellogg's  American  Insects  and 
Sharp's  Insects)  has  enabled  the  author  to  omit  the  multitudinous 
details  of  classification  and  to  introduce  much  material  that  hitherto 
has  not  appeared  in  text-books. 

As  a  rule,  only  the  commonest  kinds  of  insects  are  referred  to  in  the 
text,  in  order  that  the  reader  may  easily  use  the  text  as  a  guide  to  per- 
sonal observation. 

All  the  illustrations  have  been  prepared  by  the  author,  and  such  as 
have  been  copied  from  other  works  are  duly  credited. 

To  Dr.  S.  A.  Forbes  the  author  is  especially  indebted  for  the  use  of 
literature,  specimens  and  drawings  belonging  to  the  Illinois  State 
Laboratory  of  Natural  History. 

Permission  to  copy  several  illustrations  from  Government  publica- 
tions was  received  from  Dr.  L.  O.  Howard,  Chief  of  the  Bureau  of  Ento- 
mology; Dr.  C.  Hart  Merriam,  Chief  of  the  Division  of  Biological 
Survey,  and  Dr.  Charles  D.  Walcott,  Director  of  the  U.  S.  Geological 
Survey.  Several  desired  books  were  obtained  from  F.  M.  Webster, 
of  the  Bureau  of  Entomology. 

Acknowledgments  for  the  use  of  figures  are  due  also  to  Dr.  E.  P. 
Felt,  State  Entomologist  of  New  York;  Dr.  E.  A.  Birge,  Director  of  the 
Wisconsin  Geological  and  Natural  History  Survey;  Prof.  E.  L.  Mark 
and  Prof.  Roland  Thaxter,  of  Harvard  University;  Prof.  J.  H.  Comstock 
of  Cornell  University;  Prof.  C.  W.  Woodworth  of  the  University  of 
California;  Prof.  G.  Macloskie  of  Princeton  University;  Prof.  W.  A. 
Locy  of  Northwestern  University;  Prof.  J.  G.  Needham  of  Cornell  Uni- 
versity; Dr.  George  Dimmock  of  Springfield,  Mass.;  Dr.  Howard  Ayers 
of  Cincinnati,  Ohio;  Dr.  W.  M.  Wheeler  of  the  American  Museum  of 
Natural  History,  New  York  City;  Dr.  W.  L.  Tower  of  the  University 
of  Chicago;  Dr.  A.  G.  Mayer,  Director  of  the  Marine  Biological  Lab- 
oratory, Tortugas,  Fla.;  James  H.  Emerton  of  Boston,  Mass.;  Dr.  and 

V 


VI  PREFACE 

Mrs.  G.  W.  Peckham  of  Milwaukee,  Wis.;  Dr.  William  Trelease, 
Director  of  the  Missouri  Botanical  Garden;  Dr.  Henry  Skinner,  as 
editor  of  "Entomological  News;"  and  the  editors  of  "The  American 
Naturalist." 

Acknowledgments  are  further  due  to  the  Boston  Society  of  Natural 
History,  the  American  Philosophical  Society  and  the  Academy  of 
Science  of  St.  Louis. 

Courteous  permission  to  use  certain  figures  was  given  also  by  The 
Macmillan  Co.;  Henry  Holt  &  Co.;  Ginn  &  Co.;  Prof.  Carl  Chun  of 
Leipzig;  F.  Diimmler  of  Berlin,  publisher  of  Kolbe's  Einfiihrung;  and 
Gustav  Fischer  of  Jena,  publisher  of  Hertwig's  Lehrbuch  and  Lang's 
Lehrbuch. 

The  first  edition,  which  was  translated  into  Japanese  by  Professors 
Miyake  and  Uchida,  has  had  a  large  sale  in  Japan. 

The  second  edition  contained  much  new  matter,  particularly  a 
chapter  on  the  transmission  of  diseases  by  insects. 

This  third  edition  has  been  brought  up  to  date  by  ^he  addition  of  a 
great  deal  of  new  material,  including  a  few  new  illustrations.  Some  two 
hundred  and  fifty  titles  have  been  added  to  the  bibliography  but,  to 
accommodate  these,  it  was  necessary  to  discontinue  other  titles  of  less 
importance. 

A  new  chapter,  on  insect  ecology,  is  given.  This  ought  to  prove 
useful,  as  the  literature  of  the  subject  is  scattered,  and  there  has  been 
no  similar  comprehensive  treatment  of  ecology  from  the  viewpoint  of 
the  entomologist. 

In  the  preparation  of  this  chapter  the  author  has  been  fortunate  in 
having  the  expert  advice  of  Professor  V.  E.  Shelford,  of  the  University 
of  Illinois;  who  is  not  responsible,  however,  for  any  possible  short- 
comings in  the  chapter. 

The  following  scientific  men  also  have  gladly  assisted  by  giving 
desired  information: — Dr.  L.  O.  Howard,  chief  of  the  Bureau  of  Ento- 
mology; Mr.  A.  F.  Burgess,  of  the  Bureau  of  Entomology;  Prof.  J.  H. 
Comstock,  Cornell  University;  Prof.  A.  F.  Shull,  University  of  Michi- 
gan; Mr.  Nathan  Banks,  Museum  of  Comparative  Zoology,  Cambridge, 
Mass.;  Mr.  Charles  Macnamara,  Arnprior,  Ontario,  Canada;  Professor 
A.  O.  Weese,  University  of  New  Mexico;  Dr.  C.  P.  Alexander,  Mr.  W.  P. 
Flint  and  Dr.  H.  Yuasa,  of  the  Illinois  State  Natural  History  Survey; 
Professor  A.  D.  MacGillivray  and  Dr.  R.  D.  Glasgow,  of  the  Univer- 
sity of  Illinois. 

Permission  to  use  the  map  for  Plate  V.  was  courteously  given  by 
Dr.  B.  E.  Livingston  and  the  Carnegie  Institution  of  Washington. 


CONTENTS 

Chapter  Page 

I.  Classification ' i 

II.  Anatomy  and  Physiology 27 

III.  Development 129 

IV.  Adaptations  of  Aquatic  Insects 165 

V.  Color  and  Coloration 172 

Vl.  Adaptive  Coloration 194 

VII.  Insects  in  Relation  to  Plants 212 

VIII.  Insects  in  Relation  to  Other  Animals 233 

IX.  Transmission  of  Diseases  by  Insects 248 

X.  Interrelations  of  Insects 270 

XL  Insect  Behavior 302 

XII.  Distribution 322 

XIII.  Insect  Ecology 348 

XIV.  Insects  in  Relation  to  Man 410 

Literature 430 

Index 479 


ENTOMOLOGY 


CHAPTER  I 

CLASSIFICATION 

At  tJie  outset  it  is  essential  to  know  where  insects  stand  in  relation  to 
other  animals. 

Arthropoda. — Comparing  an  insect,  a  centipede  and  a  crayfish 
with  one  another,  they  are  found  to  have  certain  fundamental  characters 
in  common.  All  are  bilaterally  symmetrical,  are  composed  of  a  linear 
series  of  rings,  or  segments,  bearing  paired,  jointed  appendages,  and 
have  an  external  skeleton,  consisting  largely  of  a  peculiar  substance 
known  as  chitin. 

If  the  necessary  dissections  are  made,  it  can  be  seen  that  in  each  of 
these  types  the  alimentary  canal  is  axial  in  position;  above  it  extends 


Fig.  1. — Diagram  to  express  the  fundamental  structure  of  an  arthropod,  a,  antenna; 
al,  alimentary  canal;  b,  brain;  d,  dorsal  vessel;  ex,  exoskeleton;  I,  limb;  n,  nerve  chain;  s, 
subcesophageal  ganglion. — After  Schmeil. 

the  dorsal  blood  vessel  and  below  Hes  the  ventral  ladder-like  series  of 
segmental  ganglia  and  paired  nerve  cords,  or  commissures;  between  the 
commissures  that  connect  the  brain  and  the  subcesophageal  ganglion 
passes  the  oesophagus.  These  relations  appear  in  Figs,  i  and  165. 
Furthermore,  the  sexes  are  almost  invariably  separate  and  the  primary 
sexual  organs  consist  of  a  single  pair. 

No  animals  but  arthropods  have  all  these  characters,  though  the 
segmented  worms,  or  annelids,  have  some  of  them^ — for  example  the 
segmentation,  dorsal  heart  and  ventral  nervous  chain.  On  account  of 
these  correspondences  and  for  other  weighty  reasons  it  is  believed  that 

I 


ENTOMOLOGY 


arthropods  have  descended  from  annelid-Hke  ancestors.  Annelids, 
however,  as  contrasted  with  arthropods,  have  segments  that  are  essen- 
tially ahke,  have  no  external  skeleton  and  never  have  paired  limbs  that 
are  jointed. 

Classes  of  Arthropoda. — Excluding  the  king-crab,  trilobites  and  a 
few  other  forms  that  have  no  im- 
mediate entomological  importance, 
the  remaining  arthropods  fall  into  nine 
classes,  which  are  characterized  as 
follows : 

Crustacea. — Aquatic,  as  a  rule. 
Head  and  thorax  often  united  into  a 
cephalo  thorax.  Numerous  paired 
appendages,  typically  biramous  (Y- 
shaped) ;  abdominal  limbs  often  pres- 
ent.  Two  pairs  of  antennae. 
Respiration  branchial  (by  means  of 
gills)  or  cutaneous  (directly  through 
the  skin).  The  exoskeleton  contains 
carbonate  and  phosphate  of  lime  in 
addition  to  chitin.  Example,  crayfish. 
Arachnida. — Terrestrial.  Usually 
two  regions,  cephalothorax  and  abdo- 
men; though  various  Acarina  have  but 
one  and  Solpugida  have  all  three— head, 
thorax  and  abdomen.  Cephalothorax 
unsegmented,  bearing  two  pairs  of  oral 
Natural  appendages  and  four  pairs  of  legs. 
Eyes  simple.  Abdomen  segmented  or 
not,  limbless.  Respiration  tracheal,  by  means  of  book-leaf  tracheae, 
tubular  tracheae,  or  both;  stigmata  almost  always  abdominal,  at 
most  four  pairs.  Heart  abdominal  in  position.  Example,  Buthus 
(Fig.  2). 

Onychophora. — Terrestrial.  Vermiform  (worm-like),  unsegmented 
externally.  One  pair  of  ringed  antennae,  a  pair  of  jaws  and  a  pair  of 
oral  shme  papillae.  Legs  numerous,  paired,  imperfectly  segmented. 
Respiration  by  means  of  short  tubular  tracheae,  the  stigmata  of  which 
are  scattered  over  the  surface  of  the  body,  or  arranged  in  rows.  Genital 
opening  posterior.  Numerous  nephridia  (excretory)  are  present, 
arranged   segmentally  in  pairs.     Two  separate  longitudinal  nerve  cords. 


-A  scorpion,  Buthus. 
size. 


CLASSIFICATION  3 

connected  by   transverse  commissures.     Integument  delicate.     Some 
fifty  species  are  known.     Example,  Peripatus  (Fig.  3). 

Diplopoda. — Terrestrial.  Two  regions,  head  and  body.  Body 
usually  cylindrical,  with  numerous  segments,  most  of  which  are  double 
and  bear  two  pairs  of  short  limbs,  which  are  inserted  near  the  median 
ventral  line.     Eyes  simple,  antennae  short,  usually  seven-segmented, 


Fig.  3. — Peripatus   capensis.     Natural   size. — After    Moseley. 


mouth  parts  consisting  of  a  pair  of  mandibles  and  a  compound  plate, 
or  gnathochilarium.  Genital  openings  separate,  anterior  in  position 
(on  the  second  segment  of  the  body).     Example,  Spirobolus  (Fig.  4).. 

Pauropoda. —  Terrestrial.  Two  regions,  head  and  body.  Body 
elongate,  twelve-segmented,  with  nine  pairs  of  functional  legs;  each  of 
the  first  five  apparent  terga  consists  morphologically  of  two  united 
terga.  Eyes  absent,  but  a  pair  of  eye-like  spots  may  be  present. 
Antennas  characteristic;  with  four  proxi- 
mal segments  and  a  pair  of  distal 
branches  bearing  three  filaments  in  all. 
Mouth  parts  represented  by  mandibles, 
maxillae  (?)  and  labium  (?).  A  single 
genital  opening  (female)  or  a  pair  of 
openings  (male)  on  the  third  body 
segment.  Minute  arthropods,  at  most 
about  one  millimeter  in  length.  Example, 
Pauropus. 

Chilopoda. — Terrestrial.  Two  regions, 
head    and    body.     Body  long  and  flat- 
tened, with  numerous  segments,  each  of 
which  bears  a  pair  of  long  six-  or  seven- 
segmented  limbs,  which  are  not  inserted  near  the  median  line.     Eyes 
simple  and  numerous  (agglomerate  in  Scutigera)  antennae  long,  many- 
segmented.     A  pair  of  mandibles  and  two  pairs  of  maxillae.     A  single 
genital  opening,  on  the  preanal  segment.     Example,  Scolopendra  (Fig.  5) . 

Symphyla. — Terrestrial.  Two  regions,  head  and  body.  Head 
prognathous,  with  a  Y-shaped  epicranial  suture.  Eyes  few.  Antennae 
long,  multiarticulate.     Four  pairs  of  mouth  parts;  mandibles    two- 


FiG.     4. — A     diplopod,     Spirobolus 
marginatus.     Natural  size. 


4  ENTOMOLOGY 

segmented.  Body  elongate,  with  fifteen  distinct  terga,  and  eleven  or 
twelve  pairs  of  legs.  Cerci  well  developed.  Genital  opening  in  the 
third  body  segment.  One  pair  of  spiracles,  opening  on  the  head,  under 
the  antennae.  Small  arthropods  not  more  than  five  or  six  millimeters 
in  length.     Example,  Scolopendrella  (Fig.  6). 

Mjrrientomata. — Terrestrial.  Three  regions:  head,  thorax  and 
abdomen.  Head  small,  conical,  prognathous.  One  pair  of  eye-like 
spots.  Antennae  absent.  Mouth  parts  suctorial.  Mandibles  and 
maxillae  attenuate,  styliform,  protrusible  and  retractile.  Labium 
attenuate.  Body  strongly  elongate,  fusiform,  narrowing  posteriorly, 
fifteen-segmented  in  adults.  Thorax  distinct  from  abdomen;  prothorax 
shorter  than  meso-  or  metathorax.  Three  pairs  of  thoracic  legs,  and  a 
pair  of  vestigial  legs  on  each  of  the  first  three  abdominal  segments. 
Last  four  abdominal  segments  more  or  less  retractile.  Cerci  absent. 
Genital  opening  posterior.  Male  genitalia  elongate,  retractile,  distally 
bilobed,  with  a  pair  of  slender,  forceps-like  appendages.  Female  appen- 
dage short,  with  short  forceps.  Minute  delicate  arthropods,  seldom 
more  than  one  millimeter  in  length.     Example,  Acerentomon  (Fig.  8.) 

A  single  order,  Protura,  discovered  and  named  by  Silvestri,  and 
consisting  of  two  families:  Acerentomidae,  without  a  tracheal  system, 
and  Eosentomidae,  with  simple  tracheae  and  two  pairs  of  thoracic 
spiracles.  Protura,  easily  overlooked  on  account  of  their  small  size,  are 
doubtless  widely  distributed.  At  present  twelve  species  are  known  from 
Europe  and  twelve  from  the  United  States,  all  but  one  of  our  species 
having  been  described  by  Dr.  H.  E.  Ewing. 

Insecta  (Hexapoda). — Primarily  terrestrial.  Three  distinct  regions 
— head,  thorax  and  abdomen.  Head  with  a  pair  of  compound  eyes  in 
most  adults,  one  pair  of  antennae  and  typically  three  pairs  of  mouth 
parts — mandibles,  maxillae  and  labium — besides  which  a  hypopharynx, 
or  tongue,  is  present.  In  Apterygota  a  fourth  pair  of  mouth  parts  is 
associated  with  the  hypopharynx.  Thorax  with  a  pair  of  legs  on  each 
of  its  three  segments  and  usually  a  pair  of  wings  on  each  of  the  posterior 
two  segments;  though  there  may  be  only  one  pair  of  wings  (as  in  Diptera, 
male  Coccidae  and  male  Strepsiptera) ;  the  prothorax  never  bears  wings. 
Abdomen  typically  with  eleven  segments  and  without  legs,  excepting  in 
some  larvae  (as  those  of  Lepidoptera,  Tenthredinidae  and  Panorpidae). 
Stigmata  paired  and  segmentally  arranged.  A  metamorphosis  (direct 
or  indirect)  occurs  except  in  Thysanura  and  Collembola. 

Relationships. — The  interrelationships  of  the  classes  of  Arthropoda 
form  an  obscure  and  highly  debatable  subject. 


CLASSIFICATION 


5 


Crustacea  and  Insecta  agree  in  so  many  morphological  details  that 
their  resemblances  can  no  longer  be  dismissed  as  results  of  a  vague 
''parallelism,"  or  "convergence"  of  development,  but  are  inexplicable 
except  in  terms  of  community  of  origin,  as  Carpenter  has  insisted. 

Arachnida  are  extremely  unhke  other  arthropods  but  find  their 
nearest  allies  among  Crustacea,  particu- 
larly the  fossil  forms  known  as  trilobites. 

Onychophora,  as  represented  by  Peri- 
patus,  are  often  spoken  of  as  bridging  the 
gulf  that  separates  Insecta,  Chilopoda  and 
Diplopoda  from  Annelida.  Peripatus  in- 
deed resembles  the  cha^topod  annelids  in 
its  segmentally  arranged  nephridia,  der- 
momuscular  tube,  coxal  glands  and  soft 
integument,  and  resembles  the  three  other 
classes  in  its  tracheae,  dorsal  vessel  with 
paired  ostia,  lacunar  circulation,  mouth 
parts  and  salivary  glands.  These  resem- 
blances are  by  no  means  close,  however, 
and  Peripatus  does  not  form  a  direct  link 
between  the  other  tracheate  arthropods 
and  the  annelid  stock,  but  is  best  regard- 
ed as  an  offshoot  from  the  base  of  the 
arthropodan  stem. 

In  speaking  of  annelid  ancestors,  none 
of  the  recent  annelids  are  meant,  of  course, 
but  reference  is  made  to  the  primordial 
stock  from  which  recent  annelids  them- 
selves have  been  derived. 

Though  Diplopoda  and  Chilopoda  have 
long  been  grouped  together  under  the  name 
Myriopoda,  they  really  have  so  little  in 
common,  beyond  the  numerous  limb-bearing  segments  and  the  charac- 
ters that  are  possessed  by  all  tracheate  arthropods,  that  their  differences 
entitle  them  to  rank  as  separate  classes.  Chilopoda  as  a  whole  are 
more  nearly  related  to  Insecta  than  are  Diplopoda,  as  regards  seg- 
mentation, mouth  parts,  tracheae,  genital  openings  and  other  characters. 

Scolopendrella,  now  placed  in  a  class  by  itself,  Symphyla,  presents  a 
remarkable  combination  of  diplopodan  and  insectean  characters. 
Scolopendrella  (Fig.  6)  and  the  thysanuran  Campodea  have  the  same 


Fig.  s. — A  centipede,  Scolopen- 
dra  heros.  About  two-thirds  the 
maximum  length. 


ENTOMOLOGY 


kind  of  head,  with  long  moniliform  antennae,  and  agree  in  the  general 
structure  of  the  mouth  parts;  the  number  of  body  segments  is  nearly 
the  same,  the  legs  and  claws  are  essentially  alike,  and  cerci  and  paired 
abdominal  stylets  are  present  in  the  two  genera,  not  to  mention  the 


Fig.  6. — Section  of  Scolopendrella  immaculata,  b,  brain;  c,  coxal  gland;  /,  fore  intes" 
tine;  h,  hind  intestine;  m,  mid-intestine;  n,  nerve  chain;  o,  opening  of  silk  gland;  od,  oviduct; 
ov,  ovary;  s,  silk  gland;  u,  urinary  tube. — After  Packard. 

correspondences  of  internal  organization.  Indeed,  it  is  highly  prob- 
bable,  as  Packard  maintained,  that  the  most  primitive  insects,  Thysa- 
nura  (and  consequently  all  other  insects),  originated  from  a  form  much 
like  Scolopendrella.  A  singular  thysanuran,  Anajapyx  vesiculosus 
(Fig.  7)  was  discovered  by  Silvestri,  who  regarded 
it  as  being  in  many  respects  the  most  primitive  in- 
sect known,  combining  as  it  does  characters  of 
Symphyla,  Diplopoda  and  Campodea. 

Silvestri  discovered  also  a  peculiar  arthropod, 
Acerentomon  doderoi  (Fig.  8)  for  which  he  made  a 
new  order — Protura.  Berlese  added  two  genera  to 
this  order,  namely,  Eosentomon  and  Acerentulus ;  and 
according  to  good  authority  Protapteron  indicum 
Schepotieff  belongs  to  the  former  genus.  Silvestri, 
followed  by  Borner,  put  Protura  among  Aptery- 
gota;  but  Berlese,  who  grouped  these  forms  under 
the  name  of  Myrientomata,  found  that  they  had 
myriopodan  as  well  as  insectean  affinities;  and 
Rimsky-Korsakow  argued  that  Myrientomata 
cannot  be  rightly  regarded  as  insects,  but  logically 
constitute  a  class  by  themselves;  and  that  this  class 
does  not  form  a  direct  link  between  myriopods  and 
insects,  but  that  all  these  groups  came  from  the  same  ancestral 
stock.  Protura  have  actually  little  in  common  with  insects;  the  pecu- 
liar structure  of  the  mouth  parts  and  genitalia  excluding  them  from 
the  group  Apterygota. 


Fig.  7. — Anajapyx 
vesiculosus.  Length,  2 
mm. — After  Silvestri. 


CLASSIFICATION 


The  following  diagram  (Fig.  9)  expresses  very  crudely  one  view  as 
to  the  annelid  origin  of  the  chief  classes  of  Arthropoda. 

The  naturalness  of  the  phylum  Arthropoda  was  questioned  by 
Kingsley  and  Packard.  The  latter  author  divided  Arthropoda  into 
five  independent  phyla,  holding  that  "there  was  no  common  ancestor 
of  the  Arthropoda  as  a  whole,  and  that  the  group  is  a  polyphyletic  one." 
This  iconoclastic  view,  however,  by  emphasizing  unduly  the  structural 
differences  among  arthropods,  tends  to  conceal  the 
many  deep-seated  resemblances  that  exist  between  the 
classes  of  Arthropoda. 

Carpenter,  in  a  most  sagacious  summary  of  the 
whole  subject  of  arthropod  relationships,  brought  to- 
gether no  little  evidence  in  favor  of  a  revised  form  of 
the  old  Miillerian  theory  of  crustacean  origins.  He 
traced  all  the  classes  of  Arthropoda  back  to  com- 
mon arthropodan  ancestors  with  a  definite  number 
of  segments  and  distinctly  crustacean  in  character; 
then  traced  these  primitive  arthropods  back  to  forms 
like  the  nauplius  larva  of  Crustacea,  and  these  in  turn 
to  a  hypothetical  form  like  the  trochosphere  larva  of 
recent  polychaete  annelids. 

Orders  of  Insects. — Linnaeus  arranged  insects  in 
seven  orders,  namely,  Coleoptera,  Hemiptera,  Lepi- 
doptera,  Neuroptera,  Hymenoptera,  Diptera  and 
Aptera.  The  wingless  insects  termed  Aptera  were 
soon  found  to  belong  to  diverse  orders  and  the  name 
has  become  so  ambiguous  as  to  meet  with  little 
approval. 

From  theLinnsean  group  Hemiptera,  the  Or thoptera  Length,  i.28nim.— 

,  ,  1        XT  1  After  SiLVESTRi. 

were  set  apart  the  old  order  Neuroptera  a  heteroge- 
neous and  unnatural  group,  was  split  into  several  distinct  orders,  and 
many  other  changes  in  the  classification  were  necessary. 

Without  entering  any  further  into  the  history  of  the  subject,  it  is 
sufficient  to  say  that  increasing  discrimination  on  the  part  of  entomolo- 
gists has  been  followed  by  a  gradual  increase  in  the  number  of  orders. 

Naturally,  the  systems  of  classification  have  grown  and  changed 
considerably,  keeping  pace  with  increasing  knowledge. 

Brauer  (1885)  made  such  important  contributions  to  the  subject  that 
his  system,  modified  more  or  less  by  Packard,  Comstock  and  others, 
has  been  followed  for  almost  forty  years. 


Pig.     8. — Aceren- 
tomon    doderoi. 


8  ENTOMOLOGY 

Handlirsch  has  made  the  most  exhaustive  investigation  of  the  phylo- 
geny  of  the  major  groups  of  insects.  His  revolutionary  system,  which 
is  based  upon  fossil  as  well  as  recent  forms,  is  of  the  kind  to  which  one 
applies  the  term  "epoch-making,"  but  is  unfortunately  so  erratic  and 
fantastic  in  some  respects  that  it  has  not  been  generally  adopted. 

As  the  orders  of  insects  have  evolved  from  one  another  in  many 
different  directions,  like  the  branches  of  a  tree,  their  natural  relation- 
ships can  not  be  expressed  correctly  in  any  linear  sequence,  like  that 
of  this  book.  Here  the  orders  are  listed  approximately  according  to 
the  degree  of  specialization,  beginning  with  the  most  primitive  insects; 


INSECTA 

CRUSTACEA              \       .CHILOPODA 

\  symphylaA/^diplopoda 
arachnidaX        / 

^ 

/ 

^MAUGOPODA 

ARTHR 

jpooj^  ANNELIDA 

Fig.  9. — Diagram  to  indicate  the  origin  of  classes  of  Arthropoda. 

and  the  attempt  is  made  to  group  together  orders  that  are  nearly 
related  to  one  another. 

In  the  course  of  the  following  synopsis  of  the  orders  of  insects  it  is 
necessary  to  use  some  terms,  as  metamorphosis  and  thysanurijorm,  in 
anticipation  of  their  subsequent  definition. 

I.  Thysanura. — No  metamorphosis.  Eyes  aggregate,  compound 
or  absent.  Antennae  long,  filiform,  multiarticulate.  Mouth  parts 
mandibulate,  either  free  (ectognathous)  or  enclosed  in  the  head  {ento- 
gnathous).  Wings  invariably  absent.  Thoracic  segments  simple 
and  similar;  prothorax  well  developed.  Abdomen  usually  elongate, 
with  ten  evident  segments  and  often  traces  of  an  eleventh  segment; 
with  two  to  eight  pairs  of  rudimentary  limbs,  or  styli,  often  accompanied 
by  eversible  ventral  sacs.  Cerci  usually  long,  filiform,  multiarticulate, 
with  frequently  a  similar  median  pseudocercus;  but  sometimes  with 


CLASSIFICATION  9 

few  segments  (Anajapyx)  or  represented  by  a  pair  of  forceps  (Japyx). 
Integument  thin;  scales  present  or  absent.  Active  and  terrestrial, 
"bristletails."  Examples,  Campodea  (Fig.  lo),  Japyx,  Machilis, 
Lepisma  (Fig.  ii),  Anajapyx  (Fig.  7).  Some  three  hundred  species  are 
known. 

2.  Collembola. — No  metamorphosis.  Eyes  ocelliform,  not  more 
than  eight  on  each  side,  often  fewer  in  number  or  absent.  Antennae 
short,  of  four  segments  in  most  genera;  five  or  six  in  a  few  genera. 
Mouth  parts  entognathous  and  typically  mandibulate,  with  occasional 
secondary  suctorial  modifications.     Wings  invariably  absent.     Tho- 


FiG.  10. — Campodea.     Length,  3  mm.  FiG.   11. — Lepisma.     Length,  10  mm. 


racic  segments  simple  and  similar,  or  prothorax  reduced.  Body  cylin- 
drical or  globular.  Ventral  tube  and  furcula  usually  present,  sometimes 
rudimentary.  Integument  delicate;  scales  present  in  some  genera. 
Small  or  minute  terrestrial  insects,  "springtails. "  Examples,  Acliorutes 
(Fig.  12),  Sminthurus  (Fig.  13).  About  nine  hundred  species  have 
been  described. 

Under  the  term  Apterygota  the  Thysanura  and  Collembola,  as  primi- 
tively wingless  insects,  are  conveniently  distinguished  from  all  other 
insects,  or  Pterygota. 

3.  Orthoptera. — Metamorphosis  direct.  Eyes  well  developed. 
Antennae  usually  filamentous,  shorter  or  much  longer  than  the  body, 
multiarticulate.     Mouth  parts  mandibulate.     Pronotum  usually  large 


ENTOMOLOGY 


(small  in  Phasmidae).  Wings  two  pairs  as  a  rule,  though  not  infre- 
quently reduced  or  absent.  Fore  wings  coriaceous  (leathery,  forming 
tegmina);  hind  pair  membranous,  ample,  closely  reticulate,  plicate 
along  the  numerous  radiating  principal  veins. 
Abdomen  with  ten  evident  segments  and  traces  of 
eleven  or  twelve.  Cerci  one-  to  eight-segmented. 
Terrestrial  and  mostly  phytophagous.  Seven 
families:  Blattidae,  Mantidae  Gryllidae,  Grylloblat- 
tidae,  Tettigoniidae  (formerly  Locustidae),  Locus- 
tidae  (formerly  Acridiidae,  Fig.  14),  Phasmidae  (Fig. 
243).  More  than  ten  thousand  species  are  known. 
4.  Dermaptera.— Metamorphosis  direct.  Eyes 
facetted,  reduced,  or  absent.  Antennae  long,  filiform, 
with  ten  to  fifty  segments  in  adults.  Mouth  parts 
mandibulate,  prognathous;  lingua  and  superlinguae 
well  developed;  labium  split  to  the  mentum;  para- 
glossa  united  with  glossa  of  same  side.  Prothorax 
large.  Thoracic  segments  distinct.  Tarsi  three- 
segmented.  Elytra  short,  'scale-like,  meeting  in  a 
straight  line.  Wings  projecting  from  under  the 
elytra,  ear-shaped,  with  many  radiating  principal 
veins,  folding  plicately,  also  twice  transversely. 
Abdomen  with  eleven  segments,  the  tergites  and 
sternites  strongly  and  complexly  imbricate  laterally,  with  a  terminal 
pair  of  forceps  (cerci).  Wingless  species  numerous.  Some  four  hun- 
dred species  are  at  present  known. 

Three  suborders,  each  represented  by  one  family :  Arixeniidae  (one 
species) ;  Hemimeridae,  containing 
a  single  African  species  (Fig.  15), 
which  is  flattened,  eyeless,  wing- 
less, with  long  unsegmented  cerci, 
viviparous,  and  parasitic  on  the  rat; 
and  Forficulidae,  formerly  a  family 
of  Orthoptera. 

5.  Platyptera. — Metamorphosis 
direct.  Mouth  parts  mandibulate. 
Wings,  if  present,  two  pairs,  delicate, 

membranous,  equal  or  hind  pair  smaller,  and  with  the  principal  veins 
few  and  simple.  Abdomen  with  usually  ten  evident  segments  and 
often  traces  of  an  eleventh.  Integument  usually  thin.  Nymphs  thy- 
sanuriform.     Five  suborders. 


Fig.  12. — The  snow 
&ea,  Achorutes  nivicola. 
Length,  2  mm. 


Sminlhiiriis    hortensis.      Length, 
1.2  mm. 


CLASSIFICATION 


Suborder  Isoptera. — Eyes  facetted,  vestigial  or  absent.     Antennae 
long  and  filamentous  or   short  and  moniliform,  nine-  to  thirty-one- 


FiG.  14. — Schistocerca    americana.     Slightly   re- 
duced. 


Fig.  15. — Hemimerus  talpoides.  Length, 
1 1.5  mm. — After  Hansen. 


segmented.  Mouth  parts  prognathous  or  hypognathous.^  Thoracic 
segments  simple,  similar  and  equal ;  pro  thorax  large,  free.  Tarsi  four-  or 
five-segmented.  Alate  or  apter- 
ous. Wings  elongate,  similar, 
equal,  membranous,  dehcate,  with 
few  veins,  sometimes  with  an  in- 
deffnite  reticulation,  with  a  char- 
acteristic basal  suture  a  ong  which 
the  wing  breaks  off;  hind  wings  not 
folded.  Abdomen  elongate,  wieh 
ten  segments  and  a  pair  of  short 
two-  to  six-segmented  eerie  In- 
tegument weak.  Social  in  habit 
and  polymorphic;  known  as  white 
ants.  Example,  Termes  (Fig. 
28o)Aboutonethousanddescribedspecies. 

Suborder  Embioptera. — Eyes   facetted.      Antennae  with   fifteen   to 
thirty-one  or  more  segments.     Mouth  partsprognathous;  with  a  labial 

^Prognathous,  directed  forward,  hypognatJwus,  directed  downward. 


Fig.  16. — Oligotoma  michaeli.     Length  10.5 
mm. — After  McLachlan. 


ENTOMOLOGY 


Fig. 


Psocus  venosus.     Length,  5  mm. 


spinneret.  Thorax  elongate;  pro  thorax  small.  Tarsi  three-segmented. 
Wings  (sometimes  absent)  two  pairs,  elongate,  similar,  equal,  mem- 
branous, delicate,  with  few  and  feebly  developed  longitudinal  and  cross 
veins;  not  folded.  Abdomen  elongate,  with  ten  segments  and  frequent- 
ly an  eleventh  tergite,  and  a  pair  of  short  stout  biarticulate  cerci. 

Integument  delicate.  Feeble  insects, 
not  social  in  habit.  Examples, 
Embia,  Oligotoma  (Fig.  i6).  Some 
twenty  species,  all  from  warm 
climates. 

Suborder  Zoraptera. — Eyes  ves- 
tigial or  absent.  Antennse  monili- 
f  orm,  nine-segmented.  Thorax  long, 
as  long  as  the  abdomen;  prothorax  large,  larger  than  the  meso-  and 
metathorax  combined.  Tarsi  two-segmented.  Apterous,  or  with  two 
pairs  of  wings;  the  fore  wings  with  a  few  irregular  veins  and  cells. 
Abdomen  with  ten  evident  segments;  the  tenth  and  eleventh  united 
dorsally.  Cerci  short,  one -segmented.  Minute,  active  forms  (little 
more  than  two  millimeters  in  length),  terrestrial, 
predaceous.  One  genus,  Zorotypus,  represented 
by  three  Oriental  species  (Africa,  Ceylon,  Java), 
one  species  from  Costa  Rica  and  two  from  the 
United  States. 

These  insects  are  most  nearly  related  to  Isop- 
tera  and  Corrodentia. 

Suborder  Corrodentia.^Eyes  facetted.  An- 
tennae filiform,  with  thirteen  to  fifty  or  more 
segments.  Mouth  parts  hypognathous.  Pro- 
thorax  reduced.  Tarsi  two-  or  three-segmented. 
Wings  present,  rudimentary  or  absent;  fore  pair  the 
larger;  veins  few  and  irregular.  Abdomen  short 
and  stout,  with  nine  or  ten  segments.  Cerci  absent. 
Integument  delicate.  Small  terrestrial  insects, 
including  the  book  lice  and  other  psocids. 
Example,  Psocus  (Fig.  17).  More  than  two  hundred  species  are 
known. 

Suborder  Mallophaga.^Small  wingless  flattened  insects  of  parasitic 
habit.  Head  large.  Eyes  of  a  few  isolated  ocelli,  or  vestigial,  or 
absent.  Antennae  three-  to  five-segmented.  Mouth  parts  prognathous. 
Prothorax  distinct;  mesothorax  often,  and  metathorax  usually,  trans- 


FiG.  18.— A 
louse,  Menopon. 
2  mm. 


CLASSIFICATION 


13 


ferred  to  the  abdominal  region.    Tarsi  one-  or  two-segmented.    Abdomen 
usually    short    and  broad,  eight-  to    ten-segmented.     Cerci   absent. 


A  B 

Fig.   19. — Pteronarcys  regalis.     A,  nymph  (after  Newport);  B.  imago.     Slightly  reduced. 


Fig.  20. — Hexagenia  variabilis.     A,  nymph;  B,  imago.     Natural  size. 

Biting  lice,  or  bird  Hce,  parasitic  on  birds  and  a  few  mammals,  feeding 
on  feathers,  hair  or  skin.  Example,  Menopon  (Fig.  18).  More  than 
fifteen  hundred  species  have  been  described. 


14 


ENTOMOLOGY 


6.  Plecoptera. — Metamorphosis    direct.     Antennae    filiform,   long, 
multiarticulate.    Mouth  parts  mandibulate.    Prothorax  large.    Wings 


Fig.  21. — Libellula  pulchella.     A,  last  nymphal  skin;  B,  imago.     Slightly  reduced. 

two  pairs,  membranous,  coarsely  and  complexly  reticulate;  equal  or 
else  hind  wings  larger  and  with  an  ample  plicate  anal  area.     Abdomen 

with  ten  segments  and  usually 
a  pair  of  long  multiarticulate 
cerci.  Integument  soft. 
Nymphs  thysanuriform, 

aquatic;  adults  unique  in 
having  tracheal  gills.  The 
stone-flies.  Example,  Ptero- 
narcys  (Fig.  19).  A  single 
family,  Perlidae,  comprising 
two  hundred  species. 

7.  Ephemerida.— Meta- 
morphosis direct.  Antennae 
bristle-like.  Mouth  parts 
mandibulate,  but  atrophied 
in  the  adult.  Prothorax 
small.  Wings  membranous,  minutely  reticulate;  hind  pair  much  the 
smaller,  rarely  absent.  Abdomen  slender,  with  ten  segments  and  three 
or  two  very  long  multiarticulate  caudal  filaments  (a  pair  of  cerci,  with 
of  ten  a  median  pseudocercus) .  Integument  delicate.  Nymphs  thysa- 
nuriform, aquatic,  with  lateral  gills.  May-flies,  or  sand-flies.  Exam- 
ple, Hexagenia  (Fig.  20).     Three  hundred  species. 

8.  Odonata. — Metamorphosis  direct.  Head  mobile;  eyes  large. 
Antennas  inconspicuous,  bristle-shaped.  Mouth  parts  mandibulate. 
Prothorax  small,  free;  meso-  and  metathorax  intimately  united. 
Tarsi  three-segmented.     Wings  four,  elongate,  subequal,  similar,  mem- 


FiG.  22. — Euthrips  tritici.     Length,    1.2   mm. 


CLASSIFICATION 


15 


branous,  minutely  reticulate,  with  characteristic  costal  joint  (nodus), 
arculus  and  triangle.  Abdomen  slender,  with  ten  segments.  Cerci 
one-segmented.     Nymphs    aquatic;    adults    predatory.     Dragon-flies 


Fig.  23. — Benacus  griseus.     Slightly  reduced. 


Fig.  24. — Head  louse, 
Pediculus  capitis,  female. 
Length,  2  mm. 


and  damsel -flies.     Example,  Lihellula  (Fig.  21).     About  two  thousand 
species  have  been  described. 


Fig.  25. — Hydrophilus  triangularis.     Natural  size. 

9.  Thysanoptera. — Metamorphosis  direct,  but  including  a  subpupal 
stage.  Eyes  well  developed.  Mouth  parts  suctorial,  in  part  asym- 
metrical.    Prothorax  long,  free.     Tarsus  one-  or  two-segmented,  ter- 


i6 


ENTOMOLOGY 


Fig.      26.— Chrysopa 
plorabunda.  Slightly 

reudced. 


minating  in  a  bladder -like  organ.  Wings  present,  rudimentary  or 
absent,  the  two  pairs  narrow,  equal,  similar,  with  few  or  no  veins  and 
fringed  with  long  hairs.  Abdomen  with  ten  segments.  Minute,  slender 
insects,  known  as  "thrips."  Example,  Euthrips  (Fig.  22).  About 
two  hundred  species  have  been  described. 

10.  Hemiptera. — Metamorphosis  direct.  Antennae  usually  few- 
segmented.     Mouth  parts  suctorial.     Prothorax  usually  large.     Wings 

usually  present,  except  in  the  parasitic  forms. 
Eighteen  thousand  species.     Two  suborders. 

Suborder  Homoptera. — Head  deflexed.  Wings 
four,  sloping  roof -like,  similar  and  membranous 
or  fore  pair  somewhat  coriaceous  (leathery) 
throughout.  Wings  absent  in  female  Coccidae;  in 
males,  fore  wings  present,  hind  wings  absent, 
represented  by  halteres.     Phytophagous  insects. 

Example,  Cicada  (Fig.  209).     Six  thousand  species. 

Suborder  Heteroptera. — Head  free,  not  deflexed.     Antennas  often 

long,  few-segmented.     Prothorax  free.     Wings  four  (sometimes  reduced 

or   absent)    folded   flat;   fore   wings   thickened  basally,   membranous 

apically  (hemelytra) ,  overlapping  obliquely;  hind  wings  membranous, 

with     large     anal    area.     Terrestrial    or 

aquatic.     The    true    "bugs."     Example, 

Benacus  (Fig.  23) .    About  twelve  thousand 

species. 

11.  Parasita.^ — Metamorphosis  direct. 
Wingless  parasites.  Eyes  simple  or  absent. 
Antennae  short,  three-  to  five-segmented. 
Prognathous.  Head  with  a  short  tubular 
beak,  crowned  with  hooks,  containing 
a  delicate  protrusible  sucking  tube.  Tho- 
racic segments  intimately  united.  Tarsus 
with  a  single  claw.  Integument  thin.  The  sucking  lice,  blood-sucking 
parasites  of  mammals,  represented  by  the  "  cooties."  Example,  Pedicu- 
lus  (Fig.  24).     Some  fifty  species  are  known. 

12.  Coleoptera. — Metamorphosis  indirect.  Ocelli  usually  absent. 
Antennae  of  various  forms,  with  segments  varying  in  number  (two  to 
twenty-seven)  but  commonly  ten  or  eleven.  Mouth  parts  mandibulate. 
Prothorax  large,  free.    Two  pairs  of  wings ;  fore  pair  horny  or  shell-hke  as 

1  Various  names  have  been  used  for  this  group,  but  the  name  which  has  priority  and 
is  sanctioned  by  longest  usage  is  Farasiia  (Latreille,  1796). 


Fig.  27. — Bittacus  slrigosus.     Nat- 
ural size. 


CLASSIFICATION 


17 


a  rule  {elytra),  meeting  in  a  straight  line;  hind  pair  membranous,  often 
folded.  Larvae  sometimes  thysanuriform,  often  eruciform,  mandibulate. 
Hard-bodied  iusects,  the  beetles.  Example,  Hydrophiliis  (Fig.  25). 
About  one  hundred  and  fifty  thousand  species. 

13.  Strepsiptera. — Hypermetamorphic;  first  larva  hexapodous,  with 
long  anal  stylets;  later  larvae  apodous,  degenerate.  Female  legless, 
larviform,  larviparous,  with  no  pupal  stage;  male  pupa  hymenopteroid, 
within  a  puparium.  Male  with  large  eyes;  antennae  seven-  to  four-seg- 
mented, flabellately  produced;  labrum  and  labium  absent;  mandibles 
ensiform;  maxillae  palpiform,  two-  or  three-segmented.  Prothorax  and 
mesothorax  greatly  reduced;  metathorax  preponderant.     One  pair  of 


Fig.  28. — Molanna  cinerea.     A,  larva;  B,  imago.      X  4  diameters. — After  Felt. 


wings,  the  metathoracic,  membranous,  with  only  radial  veins  (eight  to 
five),  folding  longitudinally.  Anterior  wings  reduced  to  balancers. 
Abdomen  ten-segmented.  Integument  thin  and  soft.  Parasitic.  About 
two  hundred  species  are  known.     Found  in  all  regions  of  the  world. 

14.  Neuroptera. — Metamorphosis  indirect.  Antennae  conspicuous. 
Mouth  parts  mandibulate.  Prothorax  large.  Wings  almost  always 
four,  membranous,  subequal  or  else  hind  pair  smaller,  complexly 
reticulate,  not  plicate,  without  large  anal  area.  Larvae  thysanuriform 
or  in  some  cases  eruciform,  and  aquatic  or  terrestrial,  predaceous. 
Example,  lace-winged  fly,  Chrysopa  (Fig.  26).  About  six  hundred 
species  have  been  named. 

15.  Mecoptera. — Metamorphosis  indirect.  Antennae  long,  filiform. 
Mouth  parts  mandibulate,  at  the  end  of  a  deflexed  rostrum,  or  beak. 
Prothorax  small.     Tarsi  five-segmented.     Wings  four,  elongate,  mem- 


l8  ENTOMOLOGY 

branous,  naked,  coarsely  reticulate,  or  else  rudimentary  or  absent. 
Larvae  eruciform,  caterpillar-like,  with  three  pairs  of  thoracic  legs  and 
often  eight  pairs  of  abdominal  prolegs,  carnivorous.  Example,  Bittacus 
(Fig.  27).    A  single  family,  Panorpidae,  comprising  but  few  known  species . 

16.  Trichoptera. — Metamorphosis  indirect.  Eyes  prominent. 
Antennae  filiform.  Mouth  parts  of  imago  rudimentary  or  imperfectly 
suctorial;  mandibles  rudimentary  or  absent.  Prothorax  small.  Tarsi 
five-segmented.  Wings  four,  membranous,  hairy,  veins  moderate  in 
number,  cross  veins  few;  hind  pair  almost  always  the  larger,  with 
pHcate  anal  area.  Larvae  suberuciform,  with  three  pairs  of  thoracic 
legs,  aquatic,  usually  case-forming.  Caddis  worms  and  caddis  flies. 
Example,  Molanna  (Fig.  28).  Between  five  and  six  hundred  species 
are  known. 

17.  Lepidoptera. — Metamorphosis  indirect.  Antennae  long,  of  vari- 
ous forms,  many-segmented.  Mouth  parts  suctorial,  mandibles  absent 
or  rudimentary  (except  in  a  few  generahzed  species).  Eyes  well 
developed.  Ocelli  sometimes  present.  Prothorax  reduced.  Tarsi 
usually  five-segmented.  Wings  four,  large,  similar,  membranous,  with 
veins  moderate  in  number,  and  few  cross  veins.  Adults  usually  clothed 
throughout  with  scales.  Larvae  eruciform  (caterpillars),  typically  with 
three  pairs  of  thoracic  legs  and  five  pairs  (sometimes  fewer)  of  abdom- 
inal prolegs,  mandibulate,  phytophagous  (rarely  carnivorous).  Butter- 
flies and  moths.  Some  fifty  thousand  species  have  been  described. 
Two  suborders,  not  sharply  separated  from  each  other. 

Suborder  Heterocera. — Antennae  of  various  forms,  but  not  ter- 
minating in  a  distinct  knob  or  club.  Frenulum  usually  present. 
Chiefly  nocturnal  in  habit.     Example,  Callosamia  (Fig.  239). 

Suborder  Rhopalocera.— Antennae  simple,  terminating  in  a  distinct 
club  and  without  conspicuous  lateral  processes.  Frenulum  absent. 
Diurnal  normally.     Examples,  Papilio  (Fig.  29),  Anosia  (Fig.  247,  A). 

18.  Hymenoptera. — Metamorphosis  indirect.  Mouth  parts  at  the 
same  time  mandibulate  and  suctorial.  Prothorax  usually  small.  Tarsi 
usually  five-segmented.  Wings  two  pairs,  similar,  membranous,  trans- 
parent or  translucent,  without  scales,  with  a  few  irregular  veins  and 
cells;  venation  sometimes  reduced;  hind  wings  smaller  than  fore  wings; 
fore  and  hind  wings  held  together  by  a  series  of  hooks  {hamuli). 
Abdomen  usually  with  six  or  seven  evident  segments.  Females  with  an 
ovipositor,  modified  for  sawing,  boring  or  stinging.  Larvae  eruciform, 
mandibulate;  caterpillar-like,  with  head  and  legs,  or  maggot-like  and 
apodous.     Twenty-five  or  thirty  thousand  species.     Two  suborders. 


CLASSIFICATION 


19 


Suborder  Terebrantia  (Phytophaga,  Sessiliventres). — Abdomen 
broadly  attached  to  the  thorax  (sessile).  Trochanters  of  posterior 
legs  two-segmented.  Ovipositor  modified  for  boring,  sawing  or  cutting. 
Larvae  with  complex  mouth  parts,  frequently  caterpillar-like,  with  three 


Pig.  29. — Papilio  troilus.     A,  larva;  B,  larva  suspended  for  pupation;  C,  chrysalis.     Nat- 
ural size. 

pairs  of  thoracic  legs  and  seven  or  eight  pairs  of  abdominal  prolegs. 
Phytophagous  or  parasitic.  Saw-flies,  gall-flies,  ichneumon-flies,  etc. 
Example,  the  pigeon  horn-tail,  Tremex  (Fig.  30). 

Suborder  Aculeata  (Heterophaga, 
Petiolata.) — Abdomen  petiolate  or 
subpetiolate  (with  a  deep  constriction 
between  the  thoracic  and  abdominal 
regions).  First  abdominal  segment 
(propodeum)  transferred  to  the  tho- 
racic region.  Trochanters  of  posterior 
legs  one-segmented.  Ovipositor  often 
modified  to  form  a  sting.  Larvae 
apodous.  Ants,  bees,  wasps,  etc.  Ex- 
ample, the  honey  bee,  Apis  (Fig.  284). 

19.  Diptera. — Metamorphosis  indi- 
rect. Mouth  parts  typically  sectorial, 
but  modified  for  piercing,  lapping, 
rasping,    etc.     Prothorax   and    meta- 

thorax  small,  mesothorax  predominant.  Tarsi  usually  five-segmented. 
One  pair  of  wings  (mesothoracic) ,  membranous,  transparent,  with 
few   veins;  wings  rudimentary  or  absent,  however,   in  most  of   the 


Pig.  30. — Tremex columba.  /I,  imago; 
B,  larva  (with  parasitic  larva  of  Thalessa 
attached).     Natural  size. — After  Riley. 


20  ENTOMOLOGY 

parasitic  species;  hind  wings  represented  by  a  pair  of  knobbed 
threads,  or  balancers.  Larvae  usually  eruciform,  with  the  head  fre- 
quently reduced  to  a  mere  vestige  with  or  without  a  pair  of  mandibles, 
and  usually  without  true  legs,  though  pseudopods  may  be  present. 
Pupa  naked,  or  enclosed  in  a  puparium.  The  flies.  Example,  crane- 
fly,  Tipula  (Fig.  31).     About  forty  thousand  described  species. 


Fig.  31. — Tipula.     A,  larva;  B,  cast  pupal  skin;  C,  imago.     Slightly  reduced. 

20.  Siphonaptera. — Metamorphosis    indirect.     Head    small,    not 
sharply   separated   from   the   thorax.     Eyes  minute   and   simple,   or 

absent.  Antennae  short  and 
stout,  situated  in  depressions. 
Mouth  parts  suctorial.  Body 
laterally  compressed.  Tho- 
racic segments  subequal,  free; 
coxae  large;  tarsi  five-segment- 
ed. Wings  absent  or  at  most 
quite  rudimentary.  Larva 
with  a  head,  mandibulate, 
apodous,  vermiform.  Adults 
saltatorial,  parasitic  on  warm- 
blooded animals.  The  well 
(Fig.  32).     One  hundred  and 


Fig.  32. — Cat  and  dog  flea,  Ctenocephalus  canis. 
A,  larva  (after  Kunckel  d'Herculais);  B,  advdt. 
Length  of  adult,  2  mm. 

Example,  Ctenocephalus 


known  fleas, 
fifty  species. 

Interrelations  of  the  Orders. — The  modern  classification  aims  to 
express  relationships,  and  these  are  most  clearly  to  be  ascertained  by  a 
comparative  study  of  the  facts  of  anatomy  and  development. 

The  most  generahzed,  or  primitive,  insects  are  the  Thysanura.  Sub- 
tracting their  special,  or  adaptive,  pecuHarities,  their  remaining  charac- 
ters may  properly  be  regarded  as  inheritances  from  some  vanished 


CLASSIFICATION  2 1 

ancestral  type  of  arthropod.  This  primordial  type,  then,  probably  had 
three  simple  and  equal  thoracic  segments  differing  but  slightly  from 
the  ten  abdominal  segments;  three  pairs  of  legs  and  no  wings;  three  pairs 
of  exposed  biting  mouth  parts;  a  pair  of  long,  many- jointed  antennas 
and  a  pair  of  cerci  of  the  same  description;  a  thin  naked  integument;  a 
simple  straight  alimentary  canal  distinctly  divided  into  three  primary 
regions;  a  ganglion  and  a  pair  of  spiracles  for  each  of  the  three  thoracic 
and  the  first  eight  abdominal  segments,  if  not  all  the  latter;  no  meta- 
morphosis; functional  abdominal  legs  and  active  terrestrial  habits. 

The  existing  form  that  best  meets  these  requirements  is  Scolopen- 
drella,  which  is  not  an  insect,  however,  but  belongs  in  the  class  Sym- 
phyla.  The  most  primitive  of  known  insects  are  Anajapyx  and  Campo- 
dea,  through  which  other  insects  trace  their  origin  to  the  stock  from 
which  Symphyla  and  Diplopoda  arose. 

There  is  not  the  slightest  evidence  to  support  the  assumption  by 
Handlirsch  that  Thysanura  and  Collembola  are  degenerate  descendants 
of  winged  ancestors.  They  are  primitively  wingless  insects  (Aptery- 
gota) ;  in  other  words,  they  originated  before  insects  acquired  wings. 

Among  Thysanura,  the  genera  Machilis  and  Lepisma  show  decided 
orthopteran  affinities;  thus  their  eyes  are  compound  and  their  mouth 
parts  strongly  orthopteran;  indeed,  the  likeness  of  Lepisma  to  a  young 
cockroach  is  striking.  According  to  Crampton,  Lepisma  leads  to 
Plecoptera  and  Ephemerida;  while  Machilis  has  suggestions  of  affinities 
with  Crustacea. 

"The  generalized  form  of  Thysanura,  and  the  manner  in  which 
it  reappears  in  the  larvae  of  other  insects,  is  the  natural  key  of  the  clas- 
sification" (Hyatt  and  Arms). 

Collembola,  though  specialized  in  several  important  ways,  all 
have  the  same  peculiar  kind  of  entognathous  mouth  parts  as  Campodea 
and  Japyx,  for  which  reason  and  many  others  it  is  believed  that  Col- 
lembola are  an  offshoot  from  the  thysanuran  stem.  Collembola  are 
not  nearly  so  primitive  as  Thysanura,  however,  for  they  have  fewer 
abdominal  segments  than  the  latter,  exhibit  much  greater  concentra- 
tion of  the  nervous  system,  and  are  uniquely  specialized  in  several 
respects,  notably  as  regards  the  ventral  tube  and  the  furcula,  or  spring- 
ing organ. 

Collembola  are  no  longer  regarded  as  a  suborder  of  Thysanura  by 
those  who  are  familiar  with  the  morphology  of  the  two  groups.  All  the 
specialists  in  Thysanura  and  Collembola  agree  in  regarding  them  as 
two  distinct  orders. 


2  2  ENTOMOLOGY 

Orthoptera  probably  arose  directly  from  the  original  thysanuri- 
form  stem.  Of  Orthoptera,  Blattidae  are  the  most  primitive,  with 
Mantidae  closely  allied  to  them.  In  a  linear  arrangement,  Gryllidae 
may  follow,  though  not  closely  related  to  Mantidae.  Between  Gryl- 
lidae and  Tettigoniidae  (formerly  Locustidae)  comes  Walker's  new  family 
Grylloblattidae,  which  a  few  authors  prefer  to  regard  as  a  new  order. 
Tettigoniidas  and  Locustidae  (formerly  Acridiidae)  belong  together. 
Phasmidae  have  some  affinities  with  Locustidae,  but  show  the  greatest 
departure  from  the  primitive  orthopteran  type. 

Dermaptera,  represented  almost  entirely  by  the  family  Forficulidae, 
which  some  authorities  still  retain  in  the  order  Orthoptera,  must  have 
come  from  the  same  ancestors  as  Orthoptera,  needless  to  say.  In 
some  respects  they  are  more  primitive  than  Orthoptera;  in  others,  more 
specialized.  Though  the  order  shows  some  thysanuran  characters, 
the  resemblance  between  a  young  earwig  and  the  thysanuran  Japyx 
(both  having  forceps,  for  example)  is  on  the  whole  superficial;  the  mouth 
parts  of  the  two  agreeing  only  in  the  broadest  way.  On  the  other  hand, 
the  resemblances  in  structure  between  Dermaptera  and  Coleoptera 
are  deep-seated.  The  dermapteran  genus  Hemimerus  has  strong 
affinities  with  the  orthopteran  family  Blattidae. 

The  suborders  of  Platyptera  are  by  some  raised  to  the  rank  of 
orders.  They  are  so  closely  related,  however,  that  it  seems  preferable 
to  the  writer  to  express  their  resemblances  by  keeping  them  together, 
rather  than  to  emphasize  their  differences  by  separating  them. 

Platyptera,  as  a  whole,  are  most  nearly  related  to  Orthoptera  on  the 
one  hand  and  to  Plecoptera  on  the  other;  Isoptera  and  Embioptera  in 
particular  being  strongly  orthopteran.  Mallophaga,  aside  from  their 
parasitic  characters,  agree  closely  with  Corrodentia,  especially  as 
regards  the  structure  of  the  head  and  mouth  parts.  The  bird  lice  are 
essentially  degenerate  descendants  of  psocid-hke  ancestors  (Snodgrass). 

Zoraptera,  represented  by  six  species  of  the  genus  Zorotypus,  is 
held  to  be  a  distinct  order  by  some  authors.  A  few  years  ago,  Zoro- 
typus would  have  been  placed  without  hesitation  among  the  termites. 
The  species  of  the  genus  are  essentially  termites,  with  a  wing  venation 
suggesting  that  of  psocids. 

Plecoptera,  which  Packard  placed  in  his  order  Platyptera,  show 
many  primitive  characters,  including  thysanuriform  nymphs. 

The  more  generalized  winged  insects  fall  naturally  into  two 
groups,  which  are  not  sharply  separated,  however:  orthopteroid  and 
plecopteroid.     The  latter  group  consists  of  the  aquatic  orders  Plecop- 


CLASSIFICATION  23 

tera,  Ephemerida  and  Odonata.  Of  these,  Plecoptera  is  probably  the 
most  generalized  order;  though  Ephemerida  has  retained  some  very- 
primitive  structures,  notably  the  paired  genital  openings  and  ducts. 

It  is  often  stated  that  Plecoptera  are  the  most  primitive  of  winged 
insec.ts.  According  to  this  view,  then,  Orthoptera  have  arisen  from 
the  plecopteran  stem.  They  show,  however,  no  evidence  of  an  aquatic 
ancestry;  and  everything  indicates  that  terrestrial  insects  preceded 
aquatic.  Doubtless  plecopteroid  and  orthopteroid  insects  both  arose 
from  a  type  that  was  winged,  with  many  wing  veins,  mandibulate,  and 
terrestrial — a  form  like  a  thysanuran  but  with  wings. 

On  the  basis  of  metamorphosis,  Plecoptera,  Ephemerida  and  Odo- 
nata form  a  natural  group,  Hemimetabola,  in  which  the  changes  in 
form  during  development  are  greater  than  in  other  Heterometabola, 
the  aquatic  nymphs  of  these  three  orders  being  termed  naiads  by 
Comstock. 

Odonata  are  naturally  placed  next  to  Ephemerida  but  are  strongly 
aberrant  forms  with  a  unique  kind  of  specialization. 

Thysanoptera  form  a  distinct  order  which  is  usually  placed  next  to 
Hemiptera,  chiefly  on  account  of  the  suctorial  mouth  parts,  though 
even  in  this  respect  there  is  no  close  agreement  between  the  two  orders. 
They  are  aberrant  and  hard  to  place.  Borner  and  Crampton  find 
resemblances  between  Thysanoptera  and  Corrodentia. 

Hemiptera  form  a  homogeneous  and  monophyletic  order,  charac- 
terized by  the  unique  shape  and  arrangement  of  the  mouth  parts, 
which  are  always  of  the  same  type  (Muir).  Hemiptera  are  somewhat 
like  Orthoptera  and  possibly  originated  with  Thysanoptera  from  some 
mandibulate  and  winged  form.  The  conversion  of  mandibulate  into 
suctorial  organs  may  be  seen  within  the  order  Collembola,  though  it  is 
improbable  that  Hemiptera  arose  from  forms  like  Collembola.  Hemip- 
tera are  exceptional  among  insects  with  a  direct  metamorphosis  in 
their  highly  developed  type  of  suctorial  mouth  parts.  Homoptera 
are  on  the  whole  more  primitive  than  Heteroptera. 

Parasita,  long  a  suborder  of  Hemiptera,  should  rank  as  an  order, 
apparently;  though  opinions  differ  in  regard  to  this. 

In  the  early  days  of  the  classification,  the  sucking  lice  and  the  biting 
lice  were  always  grouped  together,  on  account  of  their  resemblances. 
Then  it  was  found  that  these  similarities,  correlated  with  parasitic 
existence,  were  only  superficial;  and  the  two  groups  were  separated. 
Some  recent  authors  have,  however,  followed  one  another  in  the  opinion 
that  the  two  kinds  of  lice  are  closely  related  to  each  other — an  opinion 


24  ENTOMOLOGY 

that  is  surprising  in  view  of  the  many  strong  differences  of  structure 
between  the  two  groups,  particularly  as  regards  the  mouth  parts. 
Though  investigators  have  not  agreed  as  to  the  morphology  of  the 
mouth  parts  of  the  sucking  lice,  a  study  of  cross  sections  of  the  mouth 
parts  leads  to  the  conclusion  that  they  conform  fundamentally  to  the 
hemipteran  type. 

Metamorphosis  offers  the  broadest  criteria  for  the  separation  of 
insects  into  primary  groups.  All  the  orders  considered  thus  far  are 
characterized  either  by  no  metamorphosis  or  by  a  relatively  slight,  or 
so-called  direct,  or  incomplete,  transformation.  The  following  orders, 
on  the  contrary,  are  distinguished  by  an  indirect,  or  complete,  metamor- 
phosis, which  appears  in  Coleoptera  and  attains  its  maximum  develop- 
ment in  Hymenoptera  and  Diptera. 

With  Coleoptera  the  cruciform  type  of  larva  appears,  as  a  derivative 
of  the  earlier  thysanuriform  type.  The  larvae  of  Meloe,  Epicauta  (Fig. 
220)  and  other  genera  pass  from  a  thysanuriform  stage  to  an  cruciform 
condition  during  their  development. 

It  was  formerly  thought  that  the  resemblances  between  Coleoptera 
and  Dermaptera  were  superficial,  but  at  present  there  is  reason  to 
believe  that  these  two  orders  are  related.  They  agree  rather  closely 
in  structure,  especially  as  regards  the  structure  of  the  head  (Crampton) 
and  the  thoracic  sclerites  (Snodgrass).  Coleoptera  have  affinities 
with  Neuroptera  also,  that  appear  in  some  of  the  larvae  as  well  as  in  the 
adult  forms.  Coleoptera  are,  however,  more  primitive  than  Neurop- 
tera, and  are  placed  here  at  the  beginning  of  the  holometabolous  series. 

Strepsiptera  should  be  separated  from  Coleoptera  as  a  distinct 
order,  accepting  the  opinion  of  Dr.  W.  D.  Pierce,  who  has  studied  the 
group  thoroughly.  Strepsiptera  are  aberrant,  peculiarly  specialized 
forms.  The  fact  that  the  male  strepsipteran  pupa  has  the  form  of  a 
hymenopterous  pupa  may  or  may  not  be  significant. 

In  Neuroptera,  as  in  Coleoptera,  the  transition  from  the  thysanu- 
riform to  the  cruciform  type  of  larva  may  take  place  during  the  develop- 
ment of  the  individual,  as  in  the  larva  of  Mantispa. 

Neuroptera  have  kinship  with  Coleoptera;  the  structure  of  the  head, 
for  one  thing,  being  essentially  the  same  in  the  two  groups.  They 
resemble  Plecoptera  also;  thus  a  form  like  Sialis  may  have  come  from 
ancestors  like  perlids. 

All  the  orders  that  follow  are  derived  from  the  neuropteran  stem, 
in  the  opinion  of  many  authorities. 

Mecoptera  form   an  isolated  order,   though  their   caterpillar-like 


CLASSIFICATION 


25 


larvae,  with  eleven  or  twelve  pairs  of  legs,  suggest  affinities  with  Lepidop- 
tera  and,  more  remotely,  with  the  tenthredinid  Hymenoptera.  Mecop- 
tera  are  most  nearly  related  to  Neuroptera  (through  the  genus  Nemop- 
tera)  and  have  also  certain  affinities  with  Diptera  (Cramp ton). 

Trichoptera,  while  much  like  Mecoptera  in  structure  and  meta- 
morphosis, are  jindoubtedly  closely  related  to  Lepidoptera;  in  view  of 
the  extensive  and  deep-seated  resemblances  between  caddis  flies  and 
the  most  generalized  moths  (Micropterygidaj)  it  must  be  concluded  that 
Trichoptera  and  Lepidoptera  originated  from  the  same  stock,  which 
was  doubtless  neuropteroid. 


%*»> 


#      .^^ 


DIPTERA 


PLECOPTERA 
PLATYPTERA 

ORTHOPTERA 


HEMIPTERA 


THYSANURA 


CQLEOPTERA 

Fig.  33. — Genealogical  diagram  of  the  orders  of  insects. 


Hymenoptera  also  trace  their  ancestry  back  to  neuropteroid  forms. 
The  most  generalized  hymenopterous  larvae,  those  of  saw-flies,  are 
caterpillar-like;  but  the  most  specialized  larvae,  as  those  of  ants,  bees, 
wasps,  and  parasitic  Hymenoptera,  are  more  like  maggots,  in  correlation 
with  their  sedentary  mode  of  life. 

Hymenoptera  are  often  called  the  "highest"  insects,  chiefly  on 
account  of  their  highly  developed  instincts  and  social  life.  From  this 
point  of  view,  however,  the  termites  also  would  rank  high,  though 
structurally  they  belong  among  the  more  generalized  insects.  As  a 
matter  of  fact,  the  system  of  classification  is  based  necessarily  on 
structure,  and  not  on  psychology;  and  structurally  Hymenoptera  are, 
taking  everything  into  consideration,  less  specialized  than  Diptera. 

In  Diptera  the  eruciform  type  of  larva  attains  its  extreme  degree  of 


26  ENTOMOLOGY 

specialization,  as  in  the  family  Muscidae.  Such  larvae  as  those  of 
mosquitoes  are  comparatively  primitive. 

The  relationships  of  Diptera  to  other  orders  are  not  evident,  but 
the  order  is  in  some  respects  like  Mecoptera.  Diptera  possibly  came 
from  forms  like  Mecoptera,  or  both  orders  may  have  arisen  from  neu- 
ropteroid  ancestors. 

The  fleas,  Siphonaptera,  are  usually  placed  next  to  Diptera,  being 
regarded  as  degenerate  flies. 

The  preceding  diagram  (Fig.  33)  is  a  graphic  summary  of  the  gen- 
ealogy of  some  of  the  orders  of  insects.  The  central  group  (T)  is  the 
hypothetical  thysanuroid  source  of  all  insects,  including  Thysanura 
themselves.  Though  Thysanura  and  Collembola  show  no  traces  of 
wings,  even  in  the  embryo,  it  should  be  borne  in  mind  that  all  the  other 
insects  probably  had  winged  ancestors  and  that  it  is  more  reasonable  to 
assume  a  single  winged  group  as  a  starting  point  than  to  suppose  that 
wings  originated  independently  in  several  different  groups  of  insects. 


CHAPTER  II 

ANATOMY  AND  PHYSIOLOGY 

I.  Skeleton 

Number  and  Size  of  Insects. — The  number  of  insect  species  al- 
ready known  is  about  400,000  and  it  is  safe  to  estimate  the  total  number 
of  existing  species  as  at  least  one  million. 

Among  the  largest  living  species  are  the  Venezuelan  beetle,  Dynastes 
hercules,  which  is  155  mm.  long,  and  the  Venezuelan  grasshopper, 
Tropidacris  latreillei,  which  has  a  length  of  166  mm.  and  an  alar  expanse 
of  240  mm.  Among  Lepidoptera,  Attacus  atlas  of  Indo-China  spreads 
240  mm.;  Attacus  casar  oi  the  Philippines,  255  mm.;  and  the  Brazilian 
noctuid  Erebus  agrippina,  280  mm.  Some  of  the  exotic  wood-boring 
larvae  attain  a  length  of  150  mm. 

The  giants  among  insects  have  been  found  in  the  Carboniferous, 
from  which  Brongniart  described  a  phasmid  (Titanophasma)  as  being 
one-fourth  of  a  meter  long,  and  a  huge  dragon  fly  {Meganeura)  with 
a  spread  of  more  than  two  feet. 

At  the  other  extreme  are  beetles  of  the  family  Trichopterygidae, 
some  of  which  are  only  0.25  mm.  in  length,  as  are  also  certain  hymenop- 
terous  egg-parasites  of  the  families  Chalcididse  and  Proctotrypidae. 

Thus,  as  regards  size,  insects  occupy  an  intermediate  place  among 
animals;  though  some  insects  are  smaller  than  the  largest  protozoans 
and  others  are  larger  than  the  smallest  vertebrates. 

Segmentation. — One  of  the  fundamental  characteristics  of  arthro- 
pods is  their  linear  segmentation.  The  subject  of  the  origin  of  this  seg- 
mentation is  far  from  simple,  as  it  involves  some  of  the  most  difficult 
questions  of  heredity  and  variation.  As  arthropod  segmentation  is 
usually  regarded  as  an  inheritance  from  annelid-like  ancestors,  the  sub- 
ject resolves  itself  into  the  question  of  the  origin  of  the  segmented 
from  the  unsegmented  "worms."  Cope,  Packard  and  others  give  the 
mechanical  explanation  which  is  here  summarized.  In  a  thin-skinned, 
unsegmented  worm,  the  flexures  of  the  body  initiated  by  the  muscular 
system  would  throw  the  integument  into  folds,  much  as  in  the  leech, 
and  with  the  thickening  of  the  integument,  segmentation  would  appear 
from  the  fact  that  the  deposit  of  chitin  would  be  least  at  the  places  of 

27 


28  ENTOMOLOGY 

greatest  flexure,  i.  e.,  the  valleys  of  the  folds,  and  greatest  at  the  places 
of  least  flexure,  i.  e.,  the  crests  of  the  folds.  This  explanation,  which 
has  been  elaborated  in  some  detail  by  the  Neo-Lamarckians,  applies 
also  to  the  segmentation  of  the  limbs,  as  well  as  the  body. 

Head. — In  an  insect  several  of  the  most  anterior  pairs  of  primary 
appendages  have  been  brought  together  to  co-operate  as  mouth  parts 
and  sense  organs,  and  the  segments  to  which  they  belong  have  become 
compacted  into  a  single  mass — the  head^-  in  which  the  original  seg- 
mentation is  difficult  to  trace.  The  thickened  cuticula  of  the  head  forms 
a  skull,  which  serves  as  a  fulcrum  for  the  mouth  parts,  furnishes  a  base 
of  attachment  for  muscles  and  protects  the  brain  and  other  organs. 

While  the  jaws  of  most  insects  can  only  open  and  shut,  transversely, 
their  range  of  action  is  enlarged  by  movements  of  the  entire  head,  which 
are  permitted  by  the  articulation  between  the  head  and  thorax. 

As  a  rule,  one  segment  overlaps  the  one  next  behind;  but  the  head, 
though  not  a  single  segment  of  course,  never  overlaps  the  prothorax  in 
the  typical  manner,  but  is  usually  received  into  that  segment.  This 
condition,  which  may  possibly  have  been  brought  about  simply  by  the 
backward  pull  of  the  muscles  that  move  the  head,  has  certain 
mechanical  advantages  over  the  alternative  condition,  in  securing, 
most  economically,  freedom  of  movement  of  the  head  and  protection 
for  the  articulation  itself. 

The  size  and  strength  of  the  skull  are  usually  proportionate  to  the 
size  and  power  of  the  mouth  parts.  In  some  insects  almost  the  entire 
surface  of  the  head  is  occupied  by  the  eyes,  as  in  Odonata  (Fig.  21,  B) 
and  Diptera  (Fig.  40).  In  muscid  and  many  other  dipterous  larvae,  or 
"maggots,"  the  head  is  reduced  to  the  merest  rudiment. 

Though  commonly  more  or  less  globose  or  ovate,  the  head  presents 
innumerable  forms;  it  often  bears  unarticulated  outgrowths  of  various 
kinds,  some  of  which  are  plainly  adaptive,  while  others  are  apparently 
purposeless  and  often  fantastic. 

Sclerites  and  Regions  of  the  Skull. — The  dorsal  part  of  the  skull 
(Fig.  34)  consists  almost  entirely  of  the  epicranium,  which  bears  the 
compound  eyes;  it  is  usually  a  single  piece,  or  sclerite,  though  in  some 
of  the  simpler  insects  it  is  divided  by  a  Y-shaped  suture,  the  epicranial 
suture.  The  middle  of  the  face,  where  the  median  ocellus  often  occurs, 
is  termed  the  front;  ordinarily  this  is  simply  a  region,  though  a  frontal 
sclerite  exists  in  some  insects  between  the  branches  of  the  epicranial 
suture.  Just  above  the  front,  and  forming  the  summit  of  the  head,  is 
the  region  known  as  the  vertex;  it  often  bears  ocelli.     The  clypeus  is 


ANATOMY   AND   PHYSIOLOGY 


29 


easily  recognized  as  being  the  sclerite  to  which  the  upper  Hp,  or  lahrum, 
is  hinged,  though  the  clypeus  is  not  invariably  delimited  as  a  distinct 
sclerite.  In  certain  insects  a  transverse  suture  divides  the  clypeus 
into  an  anteclypeus  and  a  postdypeus.  The  cheeks  of  an  insect  are 
known  as  the  gencB,  and  post-gence  sometimes  occur.  On  the  under  side 
of  the  head  is  the  gula,  which  bears  the  under  lip,  or  labium.  That  part 
of  the  skull  nearest  the  pro  thorax  is  termed  the  occiput;  usually  it  is  not 
delimited  from  the  epicranium,  though  in  some  insects  it  is  continuous 
with  the  post-genai  to  form  a  distinct  sclerite.  The  occiput  surrounds 
the  opening  known  as  the  occipital  foramen,  through  which  the  oesopha- 


FiG.  34. — Skull  of  a  grasshopper,  Melanoplus  differenlialis.  a,  antenna;  c,  clypeus;  e, 
compound  eye;  /,  front;  g,  gena;  I,  labrum;  i^,  labial  palpus;  m,  mandible;  mp,  maxillary 
palpus;  o,  ocelli;  oc,  occiput;  pg,  post-gena;  v,  vertex. 

gus  and  other  organs  pass  into  the  thorax.  The  membrane  of  the 
neck  in  Orthoptera  and  some  other  insects  contains  small  cervical 
sclerites,  dorsal,  lateral  or  ventral  in  position;  these,  in  the  opinion  of 
Comstock,  pertain  to  the  last  segment  of  the  head.  Besides  those 
described,  a  few  other  cephalic  sclerites  may  occur,  small  and  incon- 
spicuous, but  nevertheless  of  morphological  importance;  for  example, 
ocular  or  antennal  sclerites,  bearing  the  eyes  or  the  antennas,  respec- 
tively; and  the  trochantin  of  the  mandible,  situated  between  the  mandi- 
ble and  gena. 

Tentorium. — In  the  head  is  a  chitinous  supporting  structure  known 
as  the  tentorium.  This  consists  of  a  central  plate  from  which  diverge 
either  two  or  three  pairs  of  arms  {anterior,  posterior  and  dorsal)  extending 


so 


ENTOMOLOGY 


to  the  skull  (Fig.  35).  The  central  plate,  or  body,  lies  between  the 
brain  and  the  suboesophageal  ganghon  and  under  the  oesophagus,  which 
passes  between  the  anterior  pair  of  arms.  The  tentorium  braces  the 
skull,  affords  muscular  attachments  and  holds  the  cephalic  ganglia  and 
the  oesophagus  in  place.     It  is  not  a  true  internal  skeleton,  but  arises 


Fig.  35. — Skull  of  a  grasshopper,  Dissos 
teira  Carolina,  o,  occipital  foramen;  t,  t, 
anterior  arms  of  tentorium. 


Fig.  36. 


-Head  of  a  gyrinid  beetle,  Dineutus, 
to  show  divided  eye. 


from  the  same  ectodermal  layer  which  produces  the  external  cuticula; 
though  authors  are  not  agreed  as  to  the  details  of  the  development. 

Eyes. — The  eyes  are  of  two  kinds — simple  and  compound.     The 
latter,  or  eyes  proper,  conspicuous  on  each  side  of  the  head,  are  of  com- 


FiG.  37. — Agglomerate  eyes  of  a  male  coccid, 
Leachia  fuscipennis. — After   Signoret. 


Fig.  38. — FacuU   '^^i  a  compound  eye  of 
Melanoplus.     Highly   magnified. 


mon  occurrence  except  in  the  larvae  of  most  holometabolous  insects,  in 
some  generalized  forms  (as  Collembola)  and  in  parasitic  insects.  The 
compound  eyes  (Fig.  41)  are  convex  and  often  hemispherical,  though 
their  outline  varies  greatly;  thus  it  may  be  oval  (Orthoptera)  or  triangu- 
lar (Notonecta),  while  in  the  aquatic  beetles  of  the  family  Gyrinidae 
(Fig.  36)  each  eye  has  a  dorsal  and  a  ventral  lobe,  enabhng  the  insect 
to  see  upward  and  downward  at  the  same  time ;  so  also  in  Oberea  and 


ANATOMY  AND   PHYSIOLOGY 


31 


other  terrestrial  beetles  of  the  same  family.  Superficially,  a  compound 
eye  is  divided  into  minute  areas,  or  facets,  which  though  circular  in  the 
agglomerate  type  of  eye  (Fig.  37)  are  commonly  more  or  less  hexagonal 
(Fig.  38),  as  the  result  of  mutual  pressure.  These  facets  are  not 
necessarily  equal  in  size,  for  in  dragon  flies  the  dorsal  facets  are  fre- 
quently larger  than  the  ventral.  In  diame- 
ter the  facets  range  from  .016  mm.  {Lycana) 
to  .094  mm.  {Ceramhyx).  Their  number  is 
often  enormous;  thus  the  house  fly  {Musca 
domestica)  has  4,000  to  each  eye,  a  butterfly 
{Papilio)  17,000,  a  beetle  (Mordella)  25,000 
and  a  sphingidmoth  27,000;  on  the  other  hand, 
ants  have  from  400  down,  the  worker  ant  of 
Eciton  having  at  most  a  single  facet  on  each 
side  of  the  head. 

Ocelli. — The  simple  eyes,  or  ocelli,  appear 
as  small  polished  lenses,  either  lateral  or  dor- 
sal in  position.     Lateral  ocelli  (Fig.  39)  occur 


Fig. 


39- 


^^      -Head   of   a  cater- 
in    the    larvae    of  most  holometaboloUS  insects    pillar  Samia  cecropia,  to  show 

and  in  parasitic  forms.     Dorsal  ocelli,  sup-  ^^'''^^  °'^""^- 
plementary  to  the  compound  eyes,  occur  on  or  near  the  vertex,  and 
are  more  commonly  three  in  number,    arranged  in  a  triangle,  as  in 
Odonata,  Diptera  (Fig.  40)  and  Hymenoptera  (Fig.  41)  as  well  as  many 
Orthoptera  and  Hemiptera.     Few  beetles  have  ocelli  and  almost  no 


^  A 


^-r-^^y- 


Fig.  40.^ — Ocelli  and  compound  eyes  of  a  fly,  Phormia  regina.     A,  male;  B,  female. 


butterflies  (Lerema  accius  with  its  one  ocellus  being  the  only  exception 
known),  though  not  a  few  moths  have  two  ocelli. 

As  explained  beyond,  the  compound  eyes  are  adapted  to  perceive 
form  and  movements  and  the  ocelli  to  form  images  of  objects  at  close 
range  or  simply  to  distinguish  between  Hght  and  darkness. 

Sexual  Differences  in  Eyes. — In  most  Diptera  (Fig.  40)  and  in 
Hymenoptera  (Fig.  41)  and  Ephemeridas  as  well,  the  eyes  of  the  male  are 


32 


ENTOMOLOGY 


larger  and  closer  together  (holoptic)  than  those  of  the  female  (dichoptic). 
This  difference  is  attributed  to  the  fact  that  the  male  is  more  active 


Fig.  41.— Ocelli  and  compound  eyes  of  the  honey  bee.  Apis  mellifera.     A.  queen;    B, 
drone. — After    Cheshire. 


Fig.  42. — Various  forms  of  antennae.  A,  fiUform,  Eiischistus;  B,  setaceous,  Plathemis; 
C,  moniliform,  Catogenus;  D,  geniculate,  Bombus;  f,  flagellum;  ^.pedicel;  5,  scape;  E,  irreg- 
ular, Phormia;  a,  arista;  F,  setaceous,  Galerita;  G,  clavate,  Anosia;  H,  pectinate,  male 
Ptilodaclyla;  I,  lamellate,  Lachnosterna;  J,  capitate,  Megalodacne;  K,  irregular,  DinetUus. 

than  the  female,  especially  in  the  matter  of  seeking  out  the  opposite  sex. 


ANATOMY   AND    PHYSIOLOGY  33 

Among  ants  of  the  same  species  the  different  forms  may  differ  greatly 
in  the  number  of  lateral  facets.  Thus  in  Formica  pratensis,  according  to 
Forel,  the  worker  has  about  600  facets  in  each  eye,  the  queen  800-900 
and  the  male  1,200. 

Blind  Insects. — Many  larva?,  surrounded  by  an  abundance  of  food 
and  living  often  in  darkness,  need  no  eyes  and  have  none;  this  is  true  of 
the  dipterous  "maggots"  and  many  other  sedentary  larvas,  particularly 
such  as  are  internal  parasites  (Tachinidge,  Ichneumonidae),  or  such  as 
feed  within  the  tissues  of  plants  (many  Buprestidae,  Cerambycidae  and 
CurcuHonidcE).  Subterranean  or  cavernicolous  insects  are  either 
eyeless  or  else  their  eyes  are  more  or  less  degenerate,  according  to  the 
amount  of  light  to  which  they  have 
access.  The  statement  is  made  that 
blind  insects  never  have  functional 
wings. 

Antennae. — The  antennae,  never 
more  than  a  single  pair  (though 
embryonic  "second  antennae  "  occur 
in  Thysanura  and  Collembola),  are 
situated  near  the  compound  eyes  and 
frequently  between  them.  With  rare 
exceptions  the  antennae  have  always 
several  and  usually  many  segments. 
In  form  these  organs  are  exceedingly 
varied,  though  many  of  them  may 
be  referred  to  the  types  represented  Fi^.   43.— Antennje  of  a  moth.  Samia 

cecropia.     A,  male;  B,  female. 

in  Figs.  42-44. 

Though  homologous  in  all  insects,  the  antennae  are  by  no  means  equiv- 
alent in  function.  They  are  commonly  tactile  (grasshoppers,  etc.)  or 
olfactory  (beetles,  moths)  and  occasionally  auditory  (mosquito),  as 
described  beyond,  but  may  be  adapted  for  other  than  sensory  functions. 
Thus  the  antennae  of  the  aquatic  beetle  Hydrophilus  are  used  in  connec- 
tion with  respiration  and  those  of  the  male  Meloe  to  hold  the  female. 

Sexual  Differences  in  Antennae. — In  moths  of  the  family  Saturniidee 
[S.  cecropia,  C.  promethea,  etc.)  the  pectinate  antennae  of  the  male  are 
larger  and  more  feathered  than  those  of  the  female,  and  differ  also  in 
having  more  segments  (Fig.  43).  Here  the  antennae  are  chiefly  olfac- 
tory, and  the  reason  for  their  greater  development  in  the  male  appears 
from  the  fact  that  the  male  seeks  out  the  female  by  means  of  the  sense 
of  smell  and  depends  upon  his  antennae  to  perceive  the  odor  emanating 
from  the  opposite  sex. 


34 


ENTOMOLOGY 


The  plumose  antennae  of  the  male  mosquito  (Fig.  44)  are  highly  de- 
veloped organs  of  hearing,  and  are  used  to  locate  the  female ;  they  have 
delicate  fibrillae  of  various  lengths,  some  of  which  are  thrown  into  sym- 
pathetic vibration  by  the  note  of  the  female  (p.  94). 

Meloe  has  just  been  mentioned.  In  Sminthurus  malmgrenii  (Collem- 
bola)  the  antennae  of  the  male  are  provided  with  hooks  and  otherwise 
adapted  to  grasp  those  of  the  female  at  copulation. 

Though  systematists  have  recorded  many  instances  of  antennal 
antigeny,  the  interpretation  of  these  sexual  differences  has  received  very 
little  attention;  a  beginning  in  the  subject  has  been  made  by  Schenk, 
whose  results  will  be  referred  to  in  connection  with  the  sense  organs. 


Fig.  44. — Antennae  of  mosquito,  Culex  pipiens.     A,  male;  B,  female.     The  antenna  has  a 
short  basal  segment,  not  shown  in  the  figure. 

Mouth  Parts. — On  account  of  their  great  range  of  differentiation, 
the  mouth  parts  are  of  fundamental  importance  to  the  systematist,  par- 
ticularly for  the  separation  of  insects  into  orders.  Most  of  the  orders 
fall  into  two  groups  according  as  the  mouth  parts  are  either  biting 
(mandibulate)  or  sucking  {suctorial).  Collembola  and  Hymenoptera, 
however,  combine  both  functions;  Diptera,  though  suctorial,  exhibit 
various  modifications  for  piercing,  lapping  or  rasping;  Thysanoptera 
are  partly  mandibulate  but  chiefly  suctorial;  and  adult  Ephemerida 
and  Trichoptera  have  but  rudimentary  mouth  parts. 

The  mandibulate  orders  are  Thysanura,  Collembola  (primarily), 
Orthoptera,  Dermaptera,  Isoptera,  Embioptera,  Corrodentia,  Mal- 
lophaga,  Plecoptera,  Ephemerida  (rudimentarily  in  adult),  Odonata, 
Coleoptera,  Strepsiptera,  Neuroptera  and  Mecoptera. 


ANATOMY   AND    PHYSIOLOGY 


35 


The  usual  statement  is  that  there  are  three  pairs  of  mouth  parts, 
namely,  mandibles,  maxillcB  and  labium.  As  a  matter  of  fact,  there  are 
four  pairs,  counting  the  superlingucB,  which  are  evident  in  Thysanura 
and  Collembola,  become  vestigial  in  Heterometabola,  and  disappear  in 
the  most  specialized  Holometabola.  The  mandibulate,  or  primary 
type  (Fig.  45),  from  which  the  suctorial,  or  secondary  type,  has  been 
derived,  will  be  considered  first. 

Mandibulate  Type. — The  labrum,  or  upper  lip,  in  biting  insects  is  a 
simple  plate,  hinged  to  the  clypeus  and  moving  up  and  down;  though 
capable  of  protrusion  and  retraction  to  some  extent.     It  covers  the  man- 


FiG.  45. — Mouth  parts  of  a  cockroach,  Parcoblatta  pennsylvanica.  A,  labrum;  B, 
mandible;  C,  hypopharynx;  D,  maxilla;  E,  labium;  c,  cardo;  g  (of  maxilla),  galea;  g  (of 
labium),  glossa;  /,  lacinia;  /^,  labial  palpus;  m,  mentum;  mp,  maxillary  palpus;  p,  paraglossa; 
pf,  palpifer;  pg,  palpiger;  s,  stipes;  sm,  submentum.     B,  D,  and  E  are  in  ventral  aspect. 

dibles  in  front  and  pulls  food  back  to  these  organs.  On  the  roof  of  the 
pharynx,  under  the  labrum  and  clypeus,  is  the  epipharynx;  this  consists 
of  teeth,  tubercles  or  bristles,  which  serve  in  some  insects  merely  to  hold 
food,  though  as  a  rule  the  epipharynx  in  mandibulate  insects  bears  end- 
organs  of  taste  (Packard).  The  labrum  does  not  represent  a  pair  of 
primary  appendages. 

The  mandibles,  or  jaws  proper,  move  in  a  transverse  plane,  being 
closed  by  a  pair  of  strong  adductor  muscles  and  opened  by  a  pair  of 
weaker  abductors.  The  mandible  is  almost  always  a  single  solid  piece. 
In  herbivorous  insects  (Fig.  46,  A)  it  is  compact,  bluntly  toothed,  and 


36 


ENTOMOLOGY 


often  bears  a  molar,  or  crushing,  surface  behind  the  incisive  teeth.  In 
carnivorous  species  (B)  the  mandible  is  usually  long,  slender  and  sharply 
toothed,  without  a  molar  surface.  Often,  as  in  soldier  ants,  the  man- 
dibles are  used  as  piercing  weapons;  in  bees  (C)  they  are  used  for  various 
industrial  purposes;  in  some  beetles  they  are  large,  grotesque  in  form  and 
apparently  purposeless.  The  mandibles  of  Onthophagus  (D)  and  many 
other  dung  beetles  consist  chiefly  of  a  flexible  lamella,  admirably  adapted 
for  its  special  purpose.  In  Euphoria  (Fig.  265),  which  feeds  on  pollen 
and  the  juices  of  fruits,  the  mandibles,  and  the  other  mouth  parts  as 
well,  are  densely  clothed  with  hairs.  In  the  larva  of  Chrysopa,  the 
inner  face  of  the  mandible  (Fig.  46,  E)  has  a  longitudinal  groove  against 
which  the  maxilla  fits  to  form  a  canal,  through  which  the  blood  of 


Pig.   46. — Various  forms  of  mandibles.     A,  Melanoplus;  B,  Cicindela;  C,  Apis;  D,  Onthoph- 
agus; E,   Chrysopa;  F-I,   soldier  termites   (after  Hagen). 


plant  lice  is  sucked  into  the  oesophagus.  In  termites  (F-I)  the  mandi- 
bles assume  curious  and  often  inexplicable  forms. 

Next  in  order  are  the  superlingua  {maxillulcB) ,  which  have  been 
overlooked  or  disregarded  by  most  entomologists.  The  superlinguas 
are  well  developed  in  Thysanura  and  Collembola,  particularly  the 
former  order.  In  Machilis,  for  example,  the  superlingua  has  essentially 
the  same  structure  as  a  maxilla,  as  appears  in  Fig.  47;  in  Japyx  the 
palpus  is  three-segmented  (Hansen).  The  superlinguae,  arising  in  the 
embryo  as  a  separate  pair  of  appendages  (Fig.  198,  si),  always  become 
united  by  their  bases  with  the  lingua  (Fig.  198,  In),  forming  a  pair  of 
wing-like  appendages  on  the  dorsal  side  of  the  lingua  (Figs.  50,  51). 

Among  insects,  superlinguae  are  best  developed  in  Thysanura  and 
Collembola,  and  are  known  to  occur  also  in  Orthoptera,  Dermaptera, 
Isoptera,  Corrodentia,  nymphs  of  Ephemerida  and  larvae  of  some 
Coleoptera. 

Hansen  ('93)  termed  these  appendages  "maxillulae,"  regarding 
them  as  homologous  with  the  first  maxillae  of  Crustacea;  and  in  this 


ANATOMY    AND    PHYSIOLOGY 


37 


interpretation  he  was  followed  by  others,  including  the  writer,  who 
(Folsom,  'go)  termed  them  "superlinguai."  The  writer  at  present 
agrees  with  Crampton,  however,  that  these  appendages  are  homologous 
with  the  paragnaths  of  Crustacea.  If  they  are  not  equivalent  to  the 
first  maxillae  of  Crustacea,  the  term  "maxillulae"  should  not  be  applied 
to  them;  they  may  be  termed  " superlinguse "  or  "paragnaths,"  as  one 
prefers. 

Following  the  superlinguae  are  the  maxillcB,  or  under  jaws,  which  are 
less  powerful  than  the  mandibles  and  more  complex,  consisting  as  they 
do  of  several  sclerites  (Figs.  45,  48).  Essen- 
tially, the  maxilla  consists  of  three  lobes, 
namely,  palpus,  galea  and  lacinia,  which  are 
borne  by  a  stipes,  and  hinged  to  the  skull  by 
means  of  a  cardo.  The  palpus,  always  lateral 
in  position,  is  usually  four-  or  five-segmented 
and  is  tactile,  olfactory  or  gustatory  in  function. 
The  lacinia  is  commonly  provided  with  teeth  or 
spines.  The  maxillae  supplement  the  mandi- 
bles by  holding  the  food  when  the  latter  open, 
and  help  to  comminute  the  food.  Additional 
maxillary  sclerites,  of  minor  importance,  often 
occur. 

The  labium,  or  under  lip,  may  properly  be 
likened  to  a  united  pair  of  maxillae,  for  both 
are  formed  on  the  same  three-lobed  plan. 
This  correspondence  is  evident  in  the  cock- 
roach, among  other  generalized  insects.     Thus,  in  this  insect  (Fig.  45) : 

Labium  =  Maxilla 
palpus  =  palpus 
paraglossa  =  galea 
glossa  =  lacinia 
palpiger  =  palpifer 
menium  =  stipites 
suhmentum  with  gula  =  cardines 

In  most  mandibulate  orders  the  glossae  unite  to  form  a  single  me- 
dian organ,  as  in  Harpalus  (Fig.  49,  g).  The  labium  forms  the  floor  of 
the  pharynx  and  assists  in  carrying  food  to  the  mandibles  and  maxillae. 

The  tongue,  or  hypopharynx,  is  a  median  fleshy  organ  (Fig.  45) 
which  is  usually  united  more  or  less  with  the  base  of  the  labium.     In 


Fig.  47. — Left  superlingua 
of  Machilis  variabilis.  g, 
galea;  /,  lacinia;  p,  palpus. 


38 


ENTOMOLOGY 


insects  in  general,  the  salivary  glands  open  at  the  base  of  the  hypo- 
pharynx.  In  the  most  generalized  insects,  Thysanura  and  Collembola. 
the  hypopharynx  is  a  compound  organ,  consisting  of  a  median  ventral 
lobe,  or  lingua,  and  two  dorsolateral  lobes,  termed  superlingucs  by  the 


Fig.  48. — Maxilla  of  Har pains  caliginosus, 
ventral  aspect,  c,  cardo;  g,  galea;  /,  lacinia; 
p,  palpus;  pf,  palpifer;  s,  stipes;  sg,  subgalea. 


Pig.  49. — Labium  of  Harpalus  caliginosus, 
ventral  aspect,  g,  united  glossae,  termed 
the  glossa;  m,  mentum;  p.  palpus;  pg,  palpi- 
ger;  pr,  paraglossa;  sm,  submentum.  The 
median  portion  of  the  labium  beyond  the 
mentum  (excepting  the  palpi)  is  termed  the 
ligula. 


author.  Superlinguse  occur  in  other  mandibulate  orders  just  mentioned, 
but  have  not  yet  been  recognized  in  the  most  specialized  orders  of 
insects. 


Fig.  50. — Hypopharynx  of  Hemitnerus 
talpoides.  I,  lingua;  s,  superlingua. — After 
Hansen. 


Fig.  s  i  .• — Hypopharynx  of  an  ephemerid, 
Heptagenia.  I,  lingua;  si,  si,  superlingua5. — 
After  Vayssiere. 


Suctorial  Types. — The  mandibulate  type  of  mouth  parts  is  the 
primitive  type,  from  which  the  suctorial  types  have  been  derived. 
Though  the  latter  have  evolved  in  several  directions,  they  may  all 
be  homologized  with  the  former. 


ANATOMY    AND    PHYSIOLOGY 


39 


The  suctorial,  or  haustellate,  orders,  are  CoUembola  (in  part), 
-Thysanoptera  (in  part),  Hemiptera,  Parasita,  Trichoptera  (imper- 
fectly), Lepidoptera,  Diptera,  Siphonaptera  and  Hymenoptera  (which 
have  functional  mandibles,  however). 

Hemiptera. — The  beak,  or  rostrum,  in  Hemiptera  consists  (Fig.  52) 
of  a  conspicuous,  one-  to  four-segmented  labium,  which  ensheathes  hair- 
like mandibles  and  maxillae  and  is  covered  above  at  its  base  by  a  short 


Fig.  52. — Mouth  parts  of  a  hemipteron,  Benacus  grisens.  A,  dorsal  aspect;  B,  trans- 
verse section;  C,  extremity  of  mandible;  D,  transverse  section  of  mandibles  and  maxillae 
c,  suction  canal;  I,  labrum;  li,  labium;  m,  mandible;  mx,  maxillae. 


labrum.  The  mandibles  and  maxillae  are  sharply-pointed,  piercing 
organs  and  the  former  frequently  bear  retrorse  barbs  just  behind  the 
tip ;  the  two  maxillae  lock  together  to  form  a  sucking  tube  with  two 
canals:  an  upper,  suction  canal  and  a  lower,  salivary  canal.  Though 
primarily  a  sheath,  the  labium  bears  at  its  extremity  sensory  hairs, 
which  are  doubtless  used  to  test  the  food.  This  general  description 
appUes  to  all  Hemiptera  except  the  parasitic  forms,  which  present 
special  modifications.  A  pharyngeal  pumping  apparatus  is  present, 
which  is  similar  in  its  general  plan  to  that  of  Lepidoptera  and  Diptera, 


40 


ENTOMOLOGY 


as  presently  described,  though  it  differs  as  regards  the  smaller  details  of 
construction. 

Lepidoptera.— In  Lepidoptera,  excepting  Eriocephala,  the  labrum  is 
reduced  (Fig.  53)  and  the  mandibles  are  either  rudimentary  or  absent 
(Rhopolscera).  The  two  maxillae  are  represented  by  their  galeae, 
which  form  a  conspicuous  proboscis;  the  grooved  inner  faces  of  the  galeae 
(or  laciniae,  according  to  Kellogg)  form  the  sucking  tube,  which  opens 
into  the  oesophagus.  The  labium  is  reduced,  though  the  labial  palpi 
(Fig.  54)  are  well  developed.  The  so- 
called  rudimentary  mandibles  of  Anosia 
and  other  forms  have  been  shown  by 
Kellogg  to  be  lateral  projections  of  the  la- 
brum (Fig.  53)  and  are  ^rvovfn  2i^  pilifers . 


Fig.  53. — Head  of  a  sphingid  moth,  Pro- 
toparce  sexla.  a,  antenna;  c,  clypeus;  e,  eye; 
I,  labrum;  m,  mandible;  ^,  pilifer; />r,  proboscis. 


Fig.  54. — Head  of  a  butter- 
fly, Vanessa,  a,  antennae;  I, 
labial  palpus;  p,  proboscis. 


The  exceptional  structure  of  the  mouth  parts  in  the  generalized 
genus  Eriocephala  (Micropteryx)  sheds  much  light  on  the  morphology 
of  these  organs  in  other  Lepidoptera,  as  Walter  and  Kellogg  have  shown. 
In  this  genus  there  are  functional  mandibles;  the  maxilla  presents 
palpus,  galea,  lacinia,  stipes  and  cardo,  though  there  is  no  proboscis; 
the  labium  has  well  developed  submentum,  mentum  and  palpi;  a 
hypopharynx  is  present. 

The  sucking  apparatus,  as  described  by  Burgess,  is  essentially  like 
that  of  Diptera.  Five  muscles,  originating  at  the  skull  and  inserted 
on  the  wall  of  a  pharyngeal  bulb,  serve  to  dilate  the  bulb  that  it  may 
suck  in  fluids,  while  numerous  circular  muscles  serve  by  contracting 
successively  to  squeeze  the  contents  of  the  bulb  back  into  the  stomach ; 
a  hypopharyngeal  valve  prevents  their  return  forward. 


ANATOMY    AND    PHYSIOLOGY 


41 


Diptera. — In  the  female  mosquito  the  mouth  parts  (Fig.  55)  are 
long  and  slender.  As  Dimmock  found,  the  labrum  and  epipharynx 
combine^  to  form  a  sucking  tube;  the  mandibles  and  maxillai  are  delicate, 
linear,  piercing  organs,  the  latter  being  barbed  distally;  maxillary 
palpi  are  present ;  the  hypopharynx  is  linear  also  and  serves  to  conduct 
saliva;  the  labium  forms  a  sheath,  enclosing  the  other  mouth  parts 
when  they  are  not  in  use;  a  pair  of  sensory  lobes,  termed  labella,  occur 
at  the  extremity  of  the  labium. 


Fig.  55. — Mouth  parts  of  female  mosquito,  Culex  pipiens.  A,  dorsal  aspect;  B,  trans- 
verse section;  C,  extremity  of  maxilla;  D,  extremity  of  labrum-epipharynx;  a,  antenna;  e, 
compound  eye;  h,  hypopharynx;  /,  labrum-epipharynx;  li,  labium;  tn,  mandible;  mx, 
maxilla;  p,  maxillary  palpus. — B,  after  Dimmock. 

The  oesophagus  is  dilated  to  form  a  bulb,  or  sucking  organ,  from 
which  muscles  pass  outward  to  the  skull;  when  these  contract,  the 
bulb  dilates  and  can  suck  in  fluids,  as  blood  or  water,  which  are  forced 
back  into  the  stomach  by  the  elasticity  of  the  bulb  itself,  according  to 
Dimmock;  the  regurgitation  of  the  food  is  prevented  by  a  valve. 

The  male  mosquito  rarely  if  ever  sucks  blood,  and  its  mouth  parts 
differ  from  those  of  the  female  in  having  the  mandibles  aborted  and  the 
maxillae  slightly  developed,  but  with  long  palpi,  while  the  hypopharynx 
coalesces  with  the  labium  and  there  is  no  oesophageal  bulb. 
1  Kulagin,  however,  described  them  as  remaining  separate. 


42 


ENTOMOLOGY 


Hymenoptera. — In  the  honey  bee,  which  will  serve  as  a  type,  the 
labrum  is  simple;  the  mandibles  are  well  developed  instruments  for 
cutting  and  other  purposes  (Fig.  56)  and  the  remaining  mouth  parts 
form  a  highly  complex  suctorial  apparatus,  as  follows.  The  "tongue'' 
(glossa)  is  a  long  flexible  organ,  terminating  in  a  "spoon"  {labellum, 
Figs.  56,  129)  and  clothed  with  hairs  of  various  kinds,  for  gathering 


Fig.  56. — Mouth  parts  of  the  honey  bee,  Apis  mellifera,  ventral  aspect,  c,  cardo;  g, 
ssa  (united  glossae);  I,  lorum;  lb,  labellum;  Ip,  labial  palpus;  m,  mentum;  md,  mandible; 
mp.  maxillary  palpus;  mx,  maxilla;  p,  paraglossa;  pg,  palpiger;  s,  stipes  (plus  subgalea  and 
palpifer) ;  sm,  submentum.  The  blade  of  the  maxilla  is  the  galea,  and  the  rounded  lobe 
opposite  the  palpus  is  the  lacinia. 


nectar  or  for  sensory  or  mechanical  purposes.  The  maxillae  and  labial 
palpi  form  a  tube  embracing  the  tongue,  while  the  epipharynx  fits  into 
the  space  between  the  bases  of  the  maxillae  to  complete  this  tube. 
Through  this  canal  nectar  is  driven,  by  the  expansion  and  contraction 
of  the  tube  itself,  according  to  Cheshire,  except  that  when  only  a  small 
quantity  of  nectar  is  taken,  this  passes  from  the  spoon  into  a  fine  "cen- 


ANATOMY   AND    PHYSIOLOGY 


43 


tral  duct,"  or  also  into  the  "side  ducts,"  which  are  specially  fitted  to 
convey  quantities  of  fluid  too  small  for  the  main  tube.  For  a  detailed 
account  of  the  highly  complex  and  exquisitely  adapted  mouth  parts  of 
the  honey  bee,  the  reader  is  referred  to  Cheshire's  admirable  work, 
Packard's  Text-Book,  or  Snodgrass'  The  Anatomy  of  the  Honey  Bee. 

Segmentation  of  the  Head. — The  determination  of  the  number  of 
segments  entering  into  the  composition  of  the  insect  head  has  been  a 
difficult  problem.  As  no  segment  bears  more  than  one  pair  of  primary 
appendages,  there  are  at  least  as  many  segments  in  the  head  as  there  are 


fBr.°°  o^»aj3  "aSi 


Fig.  57. — Paramedian  section  of  an  embryo  of  the  coUemboIan  Anurida  marilima;  to 
show  the  primitive  cephalic  ganglia,  i,  ocular  neuromere;  2,  antennal;  3,  intercalary; 
4,  mandibular;  5,  superlingual;  6,  maxillary;  7,  labial;  8,  prothoracic;  9,  mesothoracic;  a; 
antenna;  /,  labnim;  Zt,  labium;  U,  I'',  P,  thoracic  legs;  tn,  mandible;  mx,  maxilla.- — After 

FOLSOM. 


pairs  of  primary  appendages.  On  this  basis,  then,  the  antennae,  man- 
dibles, maxillae  and  labium  may  be  taken  to  indicate  so  many  segments; 
but  in  order  to  decide  whether  the  eyes,  labrum  and  hypopharynx  repre- 
sent segments,  other  than  purely  anatomical  evidence  is  necessary.  The 
key  to  the  subject  is  furnished  by  embryology.  At  an  early  stage  of 
development  the  future  segments  are  marked  off  by  transverse  grooves 
on  the  ventral  surface  of  the  embryo,  and  the  pairs  of  segmental  appen- 
dages are  all  alike  (Fig.  197),  or  equivalent,  though  later  they  differen- 
tiate into  antennae,  mouth  parts,  legs,  etc.     Moreover,  the  nervous 


44  ENTOMOLOGY 

system  exhibits  a  segmentation  which  corresponds  to  that  of  the  entire 
insect;  in  other  words,  each  pair  of  primitive  gangha,  constituting  a 
neuromere,  indicates  a  segment.  Now  in  front  of  the  oesophagus  three 
primitive  segments  appear,  each  with  its  neuromere  (Fig.  57):  first  in 
position,  an  ocular  segment,  destined  to  bear  the  compound  eyes; 
second,  an  antennal  segment;  third,  an  intercalary  (premandibular) 
segment,  which  in  the  generalized  orders  Thysanura  and  Collembola 
bears  a  transient  pair  of  appendages  that  are  probably  homologous  with 
the  second  antennae  of  Crustacea.  In  the  adult,  the  ganglia  of  these 
three  segments  have  united  to  form  the  brain,  and  the  original  simpli- 
city and  distinctness  have  been  lost.  The  labrum,  by  the  way,  does 
not  represent  a  pair  of  appendages,  but  arises  as  a  single  median  lobe. 
Behind  the  oesophagus,  three  embryonic  segments  are  clearly  distin- 
guishable, each  with  its  pair  of  appendages,  namely,  mandibular, 
maxillary  and  labial.  Finally,  the  hypopharynx,  or  rather  a  part  of 
it,  claims  a  place  in  the  series  of  segmental  appendages,  as  the  author 
has  maintained;  for  in  Collembola  its  two  dorsal  constituents,  or  super- 
lingucB,  develop  essentially  as  do  the  other  paired  appendages  and,  more- 
over, a  superlingual  neuromere  (Fig.  57)  exists  (even  though  Philip- 
tschenko  failed  to  find  it).  The  four  primitive  ganglia  immediately 
behind  the  mouth  eventually  combine  to  form  the  suboesophageal 
ganglion. 

To  summarize — the  head  of  an  insect  is  composed  of  at  least  six  seg- 
ments, namely,  ocular,  antennal,  intercalary,  mandibular,  maxillary 
and  labial;  and  at  most  seven,  since  a  superHngual  segment  occurs 
between  the  mandibular  and  maxillary  segments  in  Collembola  and 
Thysanura. 

Thorax. — The  thorax,  or  middle  region,  comprises  the  three  segments 
next  behind  the  head,  which  are  termed,  respectively,  pro-,  meso-  and 
metathorax.  In  aculeate  Hymenoptera,  however,  the  thoracic  mass  in- 
cludes also  the  first  abdominal  segment,  then  known  as  the  propodeum, 
or  median  segment.  Each  of  the  three  thoracic  segments  bears  a  pair 
of  legs  in  almost  all  adult  insects,  but  only  the  meso-  and  metathorax 
may  bear  wings. 

The  dift"erentiation  of  the  thorax  as  a  distinct  region  is  an  incidental 
result  of  the  development  of  the  organs  of  locomotion,  particularly  the 
wings.  Thus  in  legless  (apodous)  larvae  the  thoracic  and  abdominal 
segments  are  alike;  when  legs  are  present,  but  no  wings,  the  thoracic 
segments  are  somewhat  enlarged;  and  when  wings  occur,  the  size  of  a 
wing-bearing  segment  depends  on  the  volume  of  the  wing  muscles. 


ANATOMY    AND    PHYSIOLOGY  45 

which  in  turn  is  proportionate  to  the  size  of  the  wings.  When  wings 
are  absent  (as  in  Thysanura  and  CoUembola)  or  the  two  pairs  equal 
in  area  (as  in  Termitidae,  Odonata,  Trichoptera  and  most  Lepidoptera) 
the  meso-  and  metathorax  are  equal.  If  the  fore  wings  exceed  the 
hind  ones  (Ephemeridae,  Hymenoptera)  the  mesothorax  is  proportion- 
ately larger  than  the  metathorax;  as  also  in  Diptera,  where  no  hind 
wings  occur.  If  the  fore  wings  are  small  (Coleoptera)  or  almost 
absent  (Stylopidae)  the  mesothorax  is  correspondingly  smaller  than  the 
metathorax.  The  prothorax,  which  never  bears  wings,  may  be  enlarged 
dorsally  to  form  a  protective  shield,  as  in  Orthoptera,  Hemiptera  and 
Coleoptera;  or,  on  the  contrary,  may  be  greatly  Pes/ 

reduced,  as  in  Ephemerida,    Odonata,   Lepi- 
doptera and  Hymenoptera.     In  the  primitive  V— 7t- 
Apterygota    the   prothorax   may   become  re- 
duced (many  Collembola)  or  slightly  enlarged    P^'' 
{Lepisma) . 

The  dorsal  wall  of  a  thoracic  segment  is 
termed  the  notum,  or  tergum;  the  ventral  wall,      Pig.  58.— Diagram  of  the 
the  stermmi;  and  each  lateral  wall,  a  pleuron;  p"':^^^?^!  ^^Y"'^^  °^-^  *^°' 

'  '        J:  '     racic  segment,     ew.epimeron; 

the  restriction  of  these  terms  to  particular  es,  epistemum;  p,  prsscutum; 
segments  of  the  thorax  being  indicated  by  the  iCmr^'^^^Sum;?/.  sSSuim- 
prefixes  pro-,  meso-  or  meta-.  These  parts  are  -s^  sternum.— After  Comstock. 
usually  divided  by  sutures  into  distinct  pieces,  or  sclerites,  as  represented 
diagrammatically  in  Fig.  58.  Thus  the  tergum  of  a  wing-bearing 
segment  is  regarded  as  being  composed  of  four  sclerites  {tergites,  Fig. 
59),  namely  and  in  order,  prcescutum,  scutum,  scutellum  and  postscu- 
tellum.  The  scutum  and  scuteUum  are  commonly  evident,  but  the 
two  other  sclerites  are  usually  small  and  may  be  absent.  According 
to  Snodgrass,  the  tergum  consists  primitively  of  a  single  sclerite,  the 
notum;  the  four  sclerites  having  arisen  as  specializations;  being  not 
always  homologous  in  different  orders  of  insects.  Each  pleuron  con- 
sists chiefly  of  two  sclerites  {pleurites,  Figs.  58  and  60),  separated  from 
each  other  by  a  more  or  less  oblique  suture.  The  anterior  of  these 
two,  which  joins  the  sternum,  is  termed  the  epistemum;  the  other,  the 
epimeron.  The  former  is  divided  into  two  sclerites  in  Odonata  and 
both  are  so  divided  in  Neuroptera. 

The  sternum,  though  usually  a  single  plate,  is  in  some  instances 
divided  into  halves,  as  in  the  cockroach,  or  even  into  five  sclerites 
(Forficulidae) . 

To  these  should  be  added  the  patagia  of  Lepidoptera — a  pair  of 


46 


ENTOMOLOGY 


erectile   appendages  of  the  prothorax;  and  the  tegulce  (paraptera)  of 

Lepidoptera,  Diptera  and  Hymenoptera — a  pair  of  small  sclerites  at 

the  bases  of  the  front  wings. 

The  thorax  has  also  several  small  sclerites  which  are  not  described 

here,  though  they  are  of  interest  to  the  morphologist. 

Each  of  the  three  thoracic  segments  bears  a  pair  of  spiracles  in 

the  embryo,  but  in  most  imagines  there  are  only  two  pairs  of  thoracic 

spiracles,  the  suppressed  pair  being  the  prothoracic. 

The  sclerites  of  the  thorax  owe  their  origin  probably  to  local  strains 

on  the  integument,  brought  about  by  the  muscles  of  the  thorax.     Thus 

the  primitively  wingless  Thysanura  and 
CoUembola  have  no  hard  thoracic 
sclerites,  though  certain  creases  about 
the  bases  of  the  legs  may  be  regarded 
as  incipient  sutures,  produced  mechan- 
ically by  the  movements  of  the  legs. 
In  soft  njrmphs  and  larvae,  the  sclerites 
■0  do  not  form  until  the  wings  develop; 
and  in  forms  that  have  nearly  or  quite 
lost  their  wings,  as  Pedicuhdae,  Mallo- 
phaga,  Siphonaptera  and  some  para- 
sitic Diptera,  the  sclerites  of  the  thorax 
tend  to  disappear.  Furthermore,  the 
absence  of  sclerites  in  the  prothorax  is 


Fig.  59.— Dorsal  aspect  of  the  tho-  probably  duc  to  the  lack  of  prothoracic 

rax   of   a   beetle,    Hydrous  piceus.     1, 
pronotum;      2,     mesopraescutum;      3,    WingS 

mesoscutum;     4.     mesoscutellum;     5.    obsolete    SUturCS     of     the 
mesopostscutellum;     6,     metapraescu- 
tum;  7,  metascutum;  8,  metascutellum;    graSshoppcrs. 
9,     metapostscutellum. — After    New- 
port. 


not  withstanding    the  so-called 
pronotum   in 


Endoskeleton. — An  insect  has  no 
internal  skeleton,  strictly  speaking, 
though  the  term  endoskeleton  is  used  in  reference  to  certain  ingrowths  of 
the  external  cuticula  which  serve  as  mechanical  supports  or  as  protec- 
tions for  some  of  the  internal  organs.  The  tentorium  of  the  head  has 
already  been  referred  to.  In  the  thorax  three  kinds  of  chitinous  in- 
growths may  be  distinguished  according  to  their  positions:  (i)  phrag- 
mas,  or  dorsal  projections;  (2)  apodemes,  lateral;  (3)  furcce,  or  apo- 
physes, ventral.  The  phragmas  (Fig.  61)  are  commonly  three  large 
plates,  pertaining  to  the  meso-  and  metathorax,  and  serving  for  the 
origin  of  indirect  muscles  of  flight  in  Lepidoptera,  Diptera,  Hymenop- 
tera and  other  strong-winged  orders.     The  apodemes  are  comparatively 


ANATOMY   AND    PHYSIOLOGY 


47 


small  ingrowths,  occurring  sometimes  in  all  three  thoracic  segments, 
though  usually  absent  in  the  prothorax.  The  furcae  occur  in  each 
thoracic  segment  as  a  pair  of  conspicuous  processes,  which  either 
remain  separate  or  else  unite  more  or  less;  leaving,  however,  a  passage 
for  the  ventral  nerve  cord. 


- 

'  w 

m::.L 

/  ^  J 

t 

a 
a 

: 

Fig.  6o. — Ventral  aspect  of  a  carabid  beetle,  Galerita  janus.  i,  prosternum ;  2,  proepi- 
sternum;  3,  proepimeron;  4.  coxal  cavity;  5.  inflexed  side  of  pronotum;  6.  mesosternum;  7. 
mesoepis'ternum;  8,  mesoepimeron ;  9.  metasternum;  10,  antecoxal  piece;  11,  metaepi- 
sternum-  12,  metaepimeron;  13.  inflexed  side  of  elytron;  a.  sternum  of  an  abdominal  seg- 
ment; an.  antenna;  c,  coxa;  /,  femur;  Ip,  labial  palpus;  md.  mandible;  mp,  maxillary  pal- 
pus; /,  trochanter;  tb,  tibia;  ts,  tarsus. 

These  endoskeletal  processes  serve  chiefly  for  the  origin  of  muscles 
concerned  with  the  wings  or  legs,  and  are  absent  in  such  wingless  forms 
as  Thysanura,  Pediculidae  and  Mallophaga. 

Some  ambiguity  attends  the  use  of  these  terms.     Thus  some  writers 


48 


ENTOMOLOGY 


use  the  term  apodemes  for  furcse  and  others  apply  the  term  apodeme 
to  any  of  the  three  kinds  of  ingrowths. 

Legs. — In  almost  all  adult  insects  and  in  most  larvae  each  of  the 
three  thoracic  segments  bears  a  pair  of  legs.  The  leg  is  articulated  to 
the  sternum,  episternum  and  epimeron,  partly  by  means  of  small 
articular  sclerites  (one  of  which,  the  trochantin,  is  shown  in  Fig.  63) 
and  consists  of  five  segments  (Fig.  62),  in  the 
following  order:  coxa,  trochanter,  femur,  tibia, 
tarsus.  The  coxa  is  the  basal  segment.  The 
trochanter  is  small  and  in  parasitic  Hymenop- 
tera  consists  of  two  subsegments.  The  femur 
is  usually  stout  and  conspicuous,  the  tibia 
commonly  slender.  The  tarsus,  rarely  single- 
jointed,  consists  usually  of  five  segments,  the 
last  of  which  bears  a  pair  of  claws  in  the  adults 
of  most  orders  of  insects  and  a  single  claw  in 
larvae;  between  the  claws  in  most  imagines  is  a 
pad,  usually  termed  the  pulvillus,  or  empodium. 
Adaptations  of  Legs. — The  legs  exhibit  a 
great  variety  of  adaptive  modifications.  A 
walking '  or  running  insect,  as  a  carabid  or 
cicindelid  beetle  (Fig.  64,  A)  presents  an  aver- 
FiG.  61. -Transverse  sec-  ^ge  Condition  as  regards  the  legs.  In  leaping 
tions  of  the  thoracic  segments  insccts    (grasshoppers,    crickcts,    Haltica)    the 

of  a  beetle,  Co/Ja</z!i5,  to  show    ,  .      ,    .  ^  ^    /  ■n\ 

the  endoskeietai  processes,  hmd  fcmora  are  enlarged  {B)  to  accommodate 
A,  prothorax;  5.  mesotho-  ^j^^  powerful  cxtcusor  musclcs.     In  insccts  that 

rax;    C,    metathorax;    a,    a,  ^ 

furcae;  ad,  apodeme;  p,  make  little  use  of  their  legs,  as  May  flies  and 
p  ragma.  ter  olbe.  xipulidse,  these  appendages  are  but  weakly 
developed.  The  spinous  legs  of  dragon  flies  form  a  basket  for  catching 
the  prey  on  the  wing.  Modifications  of  the  front  legs  for  the 
purpose  of  grasping  occur  in  many  insects,  as  the  terrestrial 
families  Mantidae  (C)  and  Reduviidae  and  the  aquatic  famihes 
Belostomidae  and  Naucoridae  (D).  Swimming  species  present  special 
adaptations  of  the  legs  (Fig.  231),  as  described  in  the  chapter 
on  aquatic  insects.  In  digging  insects,  the  fore  legs  are  expanded  to 
form  shovel-like  organs,  notably  in  the  mole-cricket  (Fig.  64,  E),  in 
which  the  fore  tibia  has  some  resemblance  to  the  human  hand,  while 
the  tarsus  and  tibia  are  remarkably  adapted  for  cutting  roots,  after 
the  manner  of  shears.  The  Scarabaeidae  have  fossorial  legs,  the  anterior 
tarsi  of  which  are  in  some  genera  reduced  {F)  or  absent;  they  are  rudi- 


ANATOMY    AND    PHYSIOLOGY 


49 


-tr 


mentary  in  the  female  (G)  of  Phanceus  carnifex  and  absent  in  the  male 
{H),  and  absent  in  both  sexes  of  Deltochilum.  Though  females  of 
PhancBus  lose  their  front  tarsi  by  digging,  the  degenerate  condition  of 
these  organs  cannot  be  attributed  to  the  inheritance  of  a  mutilation, 
but  may  have  been  brought  about  by  disuse;  though  no  one  has  ex- 
plained why  the  two  sexes  should  differ  in  this 
respect.  Many  insects  use  the  legs  to  clean  the 
antennae,  head,  mouth  parts,  wings  or  legs;  the 
honey  bee  (with  other  bees,  also  ants,  Carabidae, 
etc.)  has  a  special  antenna  cleaner  on  the  front  legs 
(Fig.  267,  D),  which  is  described,  with  other  inter- 
esting modifications  of  the  legs,  on  page  229. 

Indeed,  the  legs  serve  many  such  minor  pur- 
poses in  addition  to  locomotion.  They  are  com- 
monly used  to  hold  the  female  during  coition, 
and  in  several  genera  of  Dytiscidae  (Dytiscus, 
Cyhister)  the  male  (Fig.  64,  /)  has  tarsal  disks  and 
cupules  chiefly  on  the  front  tarsi,  for  this  purpose. 


tb 


Fig.  62. — Leg  of  a  beetle,  Calo- 
soma  calidutn.  c,  coxa;  cl,  claws; 
/,  femur;  s,  spur;  t^-t^,  tarsal  seg- 
ments; tb,  tibia;  tr,  trochanter. 


Fig.  63. — Left  hind  leg  of  Bittacus. 
c,  coxa  genuina;  cm,  epimeron;  es, 
episternum;  /,  femur;  m,  trochantin;  t; 
trochanter. 


Among  other  secondary  sexual  peculiarities  of  the  legs  may  be  men- 
tioned the  tibial  brushes  of  the  male  Catocala  concumbens,  regarded  as 
scent  organs,  and  the  queer  appendages  of  male  Dolichopodid^E  that 
dangle  in  the  air  as  these  flies  perform  their  dances. 

The  pulvillus  is  commonly  an  adhesive  organ.  In  flies  it  has  glandu- 
lar hairs  that  enable  the  insects  to  walk  on  smooth  surfaces  and  to  walk 
upside  down;  so  also  in  many  beetles  and  notably  in  the  honey  bee  (Fig. 
65) ;  in  this  insect  the  pulvillus  is  released  rapidly  from  the  surface  to 
which  it  has  been  applied,  by  rolling  up  from  the  edges  inward. 

Sense  organs  occur  on  the  legs.  Thus  tactile  hairs  are  almost 
always  present  on  these  appendages,  while  auditory  organs  occur  on 
the  front  tibiae  of  Tettigoniidae,  Grylhdae  and  some  ants.     Finally,  the 


so 


ENTOMOLOGi' 


legs  may  be  used  to  produce  sound,  as  in  Stenohothrus  and  such  other 
Locustidae  as  stridulate  by  rubbing  the  femora  against  the  tegmina. 

Legs  of  Larvae.— Thoracic  legs,  terminating  in  a  single  claw,  are 
present  in  most  larvae.     Caterpillars  have,  in  addition,  fleshy  abdominal 


Fig.  64. — Adaptive  modifications  of  the  legs.  A,  Cicindela  sexguttala;  B,  Nemobius 
vittatus,  hind  leg;  C,  Stagmomantis  Carolina,  left  fore  leg;  D,  Pelocoris  femoratus,  right  fore 
leg;  E,  Gryllotalpa  borealis,  left  fore  leg;  F,  Canlhon  lavis,  right  fore  leg;  G,  PhancEus  carnifex, 
fore  tibia  and  tarsus  of  female;  H,  P.  carnifex,  fore  tibia  of  male;  /,  Dytiscus  fascivenlris, 
right  fore  leg  of  male;  c,  coxa;/,  femur;  s,  spur;  t,  trochanter;  tb,  tibia;  ts,  tarsus. 

legs   (Fig.  64)  ending  in  a  circlet  of  hooks.     Most  caterpillars  have  five 
pairs  of  these  legs  (on  abdominal  segments  3,  4,  5,  6,  and  10),  but  the 


ANATOMY    AND    PHYSIOLOGY 


51 


rest  vary  in  this  respect.  Thus  Lagoa  has  seven  pairs  (segments  2-7  and 
10)  and  Geometridae  two  (segments  6  and  10),  while  a  few  caterpillars 
{Tischeria,  Limacodes)  have  none.  Larvae  of 
saw  flies  (Tenthredinidae)  have  seven  or  eight 
pairs  of  abdominal  legs  and  larvae  of  most 
Panorpidas,  eight  pairs.  Not  a  few  coleopter- 
ous larvae  (some  Cerambycidac,  Hypera)  also 
have  abdominal  tubercles  that  represent  legs, 
but  are  incompletely  developed  as  compared 
with  those  of  Lepidoptera. 

The  legless,  or  apodous,  condition  occurs 
frequently  among  larvae  and  always  in  correla- 
tion with  a  sedentary  mode  of  life;  as  in  the 
larvae  of  many  Cerambycidae,  almost  all  Rhyn- 
chophora,  a  few  Lepidoptera,  all  Diptera,  and      Fig.  65.— Foot  of  honey  bee. 

,,  TT  ,  4-rr      4.U      ^-    -^       c-   •    ■      ^P^^  ■inellifera.     c,  c.  claws; /.. 

all  Hymenoptera  except  Ten thredmidae,  Sirici-  puiviiius;    t^-t\    tarsal    seg- 

d«,  and  other  Terebrantia.  ments.-After   Cheshire. 

Among  adult  insects,  female  scale  insects  are  exceptional  in  being 
legless. 

Walking. — An  adult  insect,  when  walking,  normally  uses  its  legs  in 
two  sets  of  three  each;  thus  the  front  and  hind  legs  of  one  side  and  the 


Fig.  66. — Caterpillar  of  Protoparce  sexta.     Natural  size. 

middle  leg  of  the  other  move  forward  almost  simultaneously — though 
not  quite,  for  the  front  leg  moves  a  Httle  before  the  middle  one,  which, 
in  turn,  precedes  the  hind  leg.  During  these  movements  the  body  is 
supported  by  the  other  three  legs,  as  on  a  tripod.  The  front  leg, 
having  been  extended  and  its  claws  fixed,  pulls  the  body  forward  by 


52 


ENTOMOLOGY 


means  of  the  contraction  of  the  tibial  flexors;  the  hind  leg,  on  the  con- 
trary, pushes  the  body,  by  the  shortening  of  the  tibial  extensors, 
against  the  resistance  afforded  by  the  tibial  spurs;  the  middle  leg  acts 
much  like  the  hind  one,  but  helps  mainly  to  steady  the  body.  Different 
species  *  show  different  peculiarities  of  gait.  In  its  analysis,  the 
walking  of  an  insect  is  rather  intricate,  as  Graber  and  Marey  have  shown. 
The  mode  of  action  of  the  principal  leg  muscles  may  be  gathered 
from  Fig.  67,  Here  the  flexion  of  the  tibia  would  cause  the  tibial  spur 
(s)  to  describe  the  line  51  ;  and  the  backward  movement  of  the  leg  due 
to  the  upper  coxal  rotator  r  would  cause  the  spur  to  follow  the  arc 
53.     As  the  resultant  of  both  these  movements,  the  path  actually 


ec  // 


Fig.  67. — Mechanics  of  an  insect's  leg.  a,  axis  of  coxa;  c,  coxa;  cl,  claw;  e,  extensor  of 
tibia;  ec,  extensor  of  claw;  et,  extensor  of  tarsus ;/,  flexor  of  tibia ;/c,  flexor  of  claw;//,  flexor 
of  tarsus;  r,  r,  rotators  of  coxa;  5,  spur;  t,  trochanter  muscle  (elevator  of  femur) ;  ti,  tibia. — 
After  Graber. 

described  by  the  tibial  spur  is  5  2 ;  then,  as  the  leg  moves  forward,  the 
curve  is  continued  into  a  loop. 

Caterpillars  use  their  legs  successively  in  pairs,  and  when  the  pairs 
of  legs  are  few  and  widely  separated,  as  in  Geometridae,  a  curious  looping 
gait  results. 

The  leg  muscles  of  a  cockroach  are  shown  in  Fig.  68. 

Leaping. — The  hind  legs,  inserted  nearest  the  center  of  gravity,  are 
the  ones  employed  in  leaping,  and  they  act  together.  A  grasshopper 
prepares  to  jump  by  bending  the  femur  back  against  the  tibia;  to  make 
the  jump,  the  tibia  is  jerked  back  against  the  ground,  into  which  the 
tibial  spurs  are  driven,  and  the  straightening  of  the  leg  by  means  of  the 
powerful  extensors  throws  the  insect  into  the  air.  At  the  distal  end  of 
the  femur  are  two  lobes,  one  on  each  side  of  the  tibia,  which  prevent 
wobbling  movements  of  the  tibia. 


ANATOMY    AND    PHYSIOLOGY 


53 


Wings. — The  success  of  insects  as  a  class  is  to  be  attributed  largely 
to  their  possession  of  wings.  These  and  the  mouth  parts,  surpassing  all 
the  other  organs  as  regards  range  of  differentiation,  have  furnished  the 
best  criteria  for  the  purposes  of  classification.  The  wings  of  insects 
present  such  countless  differences  that  an  expert  can  usually  refer  a 
detached  wing  to  its  proper  genus  and  often  to  its  species,  though  no 
fewer  than  four  hundred  thousand  species  of  insects  are  already  known. 

Typically,  there  are  two  pairs  of  wings,  at- 
tached respectively  to  the  mesothorax  and  the 
metathorax,  the  prothorax  never  bearing  wings, 
as  was  said.  When  only  one  pair  is  present  it  is 
almost  invariably  the  anterior  pair,  as  in  Diptera 
and  male  Coccidae,  though  in  male  Strepsiptera  it 
is  the  posterior  pair,  the  fore  wings  being 
rudimentary. 

In  bird  lice,  fleas  and  most  other  parasitic  in- 
sects, the  wings  have  degenerated  through  disuse. 
In  Thysanura  and  Collembola  there  are  no  traces 
of  wings  even  in  the  embryo;  whence  it  is  inferred 
that  wings  originated  later  than  these  orders  of 
insects. 

M  tiller  and  Packard  have  regarded  the  wings 

as  tergal  outgrowths;  Tower,  however,  has  shown 

that   the   wings   of    Coleoptera,    Orthoptera  and 

Lepidoptera  are  pleural  in  origin,  arising  just  below  _ 

the  line  where  later  the  suture  between  the  pleuron  left  mid  leg  of  a  cock- 
roach, posterior  aspect. 
abc,  abductor  of  coxa; 
adc,  adductor  of  coxa;  ef, 
extensor  of  tibia;  et,  ex- 
tensor of  femur; /^  flexor 
of  tibia.;  fta,  flexor  of  tar- 
sus; rl,  retractor  of  tar- 
sus.— After  MiALL  and 
Denny. 


and  tergum  will  originate,  though  the  wings  may 
subsequently  shift  to  a  more  dorsal  position. 

Modifications  of  Wings. — Being  commonly 
more  or  less  triangular,  a  wing  presents  three  mar- 
gins: front  (costal),  outer  (apical)  and  inner  (anal) ; 
and  three  angles:  humeral  (at  the  base  of  the  casta), 
apical  (at  the  apex  of  the  wing)  and  anal  (between  outer  and  inner 
margins).  Various  modifications  occur  in  the  front  wings,  which  are 
in  many  orders  more  useful  for  protection  than  for  flight.  Thus,  in 
Orthoptera,  they  are  leathery,  and  are  known  as  tegmina;  in  Coleoptera 
they  are  usually  horny,  and  are  termed  elytra;  in  Heteroptera,  the  base 
of  the  front  wing  is  thickened  and  the  apex  remains  membranous, 
forming  a  hemelytron.  Diptera  have,  in  place  of  the  hind  wings,  a 
pair    of    clubbed  threads,  known  as  balancers,  or  halteres,  and  male 


54 


ENTOMOLOGY 


Scl 


Coccidae  have  on  each  side  a  bristle  that  hooks  into  a  pocket  on  the 
wing  and  serves  to  support  the  latter.  In  many  muscid  flies  a  doubly 
lobed  membranous  squama  occurs  at  the  base  of  the  wing. 

In  Hymenoptera  the  front  and  hind  wings  of  the  same  side  are  held 
together  by  a  row  of  hooks  {hamuli);  these  are  situated  on  the  costal 
margin  of  the  hind  wing  and  clutch  a  rod-like  fold  of  the  fore  wing. 
In  very  many  moths,  the  two  wings  are  enabled  to  act  as  one  by  means 
of  a  frenulum,  consisting  of  a  spine  or  a  bunch  of  bristles  near  the  base 
of  the  hind  wing,  which,  in  some  forms,  engages  a  membranous  loop  on 
the  fore  wing. 

In  the  generalized  moths  of  the  family  Hepialidae,  the  overlapping 
fore  and  hind  wings  are  held  together  by  SLJugum,  projecting  backward 
from  the  base  of  the  fore  wing. 

Venation,  or  Neuration. — A  wing  is  divided  by  its  veins,  or  nervures, 

into    spaces,    or   cells. 
Sc2  „ .  The  distribution  of  the 

veins  is  of  great  sys- 
tematic importance, 
but  formerly,  the  ho- 
mologies of  the  veins  in 
the  different  orders  of 
insects  were  not  fixed, 
so  that  no  little  con- 
fusion resulted.  For 
example,  the  term  dis- 
cal  cell,  used  in  descriptions  of  Lepidoptera,  Diptera,  Trichoptera  and 
Psocidae,  was  in  no  two  of  these  groups  appHed  to  the  same  cell.  The 
admirable  work  of  Comstock  and  Needham,  however,  seems  to  settle 
this  disputed  subject.  By  a  study  of  the  tracheae  which  precede  and, 
in  a  broad  way,  determine  the  positions  of  the  veins,  these  authors  have 
arrived  at  a  primitive  type  of  tracheation  (Fig.  69)  to  which  the  more 
complex  types  of  tracheation  and  venation  may  be  referred. 

In  general,  the  following  principal  longitudinal  veins  may  be  distin- 
guished, in  the  following  order:  costa,  suhcosta,  radius,  media,  cubitus, 
and  anal  (Figs.  69-73). 

The  costa  (C)  strengthens  the  front  margin  of  the  wing  and  is  essen- 
tially unbranched. 

The  subcosta  {Sc)  is  close  behind  the  costa  and  is  unbranched  in  the 
imagines  of  many  orders  in  which  there  are  few  wing  veins,  though  it  is 
typically  a  forked  vein. 


3dA    2dA 


IstA 


Cu2 


Pig.  69. — Hypothetical  type  of  venation.  A,  anal  vein; 
C,  costa;  Cu,  cubitus;  M,  media;  R,  radius;  Sc,  subcosta. — 
Figs.  69-73  after  Comstock  and  Needham. 


ANATOMY   AND   PHYSIOLOGY 


55 


The  radius  (R),  though  subject  to  much  modification,  is  typically 
five-branched,  as  in  Fig.  69.  The  second  principal  branch  of  the 
radius  is  termed  the  radial  sector  (Rs) . 

The  media  (M)  is  often  three-branched  and  is  typically  four- 
branched,  according  to  Comstock  and  Needham. 

The  cubitus  (Cw)  has  two  branches. 


Fig.  70. — Wing  of  a  fly,  Rhyphus.     Lettering  as  before. 

The  anal  veins  {A)  are  typically  three,  of  which  the  first  is  usually 
simple,  while  the  second  and  third  are  many-branched  in  wings  that 
have  an  expanded  anal  area. 

The  Plecoptera,  as  a  whole,  show  the  least  departure  from  the 
primitive  type  of  venation;  which  is  well  preserved,  also,  in  the  more 
generalized  genera  of  the  Trichoptera. 

Starting  from  the  primitive  type,  specialization  has  occurred  in  two 
ways:  by   reduction  and  by 
addition.     Reduction   occurs  £ 

either  by  the  atrophy  of  veins 
or  by  the  coalescence  of  two 
or  more  adjacent  veins. 
Atrophy  explains  the  lack  of 
all  but  one  anal  vein  in 
Rhyphus  (Fig.  70)  and  other 
Diptera,  and  the  absence  of 
the  base  of  the  media  in  vl  wo-  ^^^-  ''^ 
sia  (Fig.  71)  and  many  other 
Lepidoptera;  in  the  pupa  of  Anosia,  the  media  may  be  found  com- 
plete. Coalescence  "takes  places  in  two  ways:  first,  the  point  at 
which  two  veins  separate  occurs  nearer  and  nearer  the  margin  of  the 
wing,  until  finally,  when  the  margin  is  reached,  a  single  vein  remains 
where  there  were  two  before ;  second,  the  tips  of  two  veins  may  approach 
each  other  on  the  margin  of  the  wing  until  they  unite,  and  then  the 
coalescence  proceeds  towards  the  base  of  the  wing."     (Comstock  and 


2dA 


-Wing  of  a  butterfly, 
as  before. 


A  nosia .     Lettering 


56 


ENTOMOLOGY 


Needham.)  The  former,  or  outward,  kind  of  coalescence  is  common 
in  most  orders  of  insects;  the  latter,  or  inward,  kind  is  especially 
prevalent  in  Diptera. 

Speciahzation  by  addition  occurs  by  a  multiplication  of  the  branches 
of  the  principal  veins,  or  by  the  development  of  secondary  longitudinal 
veins  between  these  branches. 

Comstock  and  Needham  have  succeeded  in  homologizing  practically 

all  the  types  of  neuration, 
including  such  perplexing 
types  as  those  of  Ephemerida 
(Fig.  72),  Odonata  (Fig.  21, 
B)  and  Hymenoptera  (Fig. 
73),  and  have  established  a 
uniform  terminology  of  the 
wing  veins.  The  system  built 
up  during  some  twenty-five 
years  by  Comstock  and  his  fol- 
lowers is  embodied  in  his  great 
volume.  The  Wings  of  Insects. 
A  student  of  the  subject  of  venation  should  consult  the  many  articles 
by  Tillyard,  a  keen  investigator,  whose  point  of  view  is  in  some  respects 
different  from  that  of  Comstock  and  Needham.  He  holds,  for  example, 
that  the  primitive  type  of  wing  had  many  veins  instead  of  few,  and 
that  the  evolutionary  tendency  has  been,  generally  speaking,  toward  a 
reduction  in  the  number  of  veins. 


Fig.   72. — Wings  of  a  May  fly.     Lettering  as  before. 


Fig.   73. — A  typical  hymenopterous   wing.     Lettering 


Folding  of  Wing. — In  some  beetles  (as  Chrysohothris)  the  wings  are 
no  larger  than  the  elytra  and  are  not  folded;  in  others  the  wings  exceed 
the  elytra  in  size,  and  when  not  in  use  are  folded  under  the  elytra  in 
ways  that  are  simple  but  efficient,  as  described  by  Kolbe  and  by  Tower. 
To  be  understood,  the  process  of  folding  should  be  observed  in  the 
living  insect.     As  described  by  Tower  for  the  Colorado  potato  beetle, 


ANATOMY   AND   PHYSIOLOGY 


57 


the  folded  wing  (Fig.  74,  B)  exhibits  a  costal  joint  (a),  a  fold  parallel 
to  the  transverse  vein  (b) ,  and  a  complex  joint  at  d.  The  wing  rotates 
upon  the  articular  head  (ah)  and  when  folded  back  beneath  the  wing- 
covers  the  inner  end  of  the  cotyla  (c)  is  brought  into  contact  with  a 
chitinous  sclerite  of  the  thorax,  which  stops  the  further  movement 
of  the  cotyla  medianward,  and  as  the  wing  swings  farther  back  the 
middle  system  of  veins  (m)  is  pushed  outward  and  anteriorly.  This 
motion,  combined  with  the  backward  movement  of  the  wing  as  a  whole, 
produces  the  folding  of  the 
distal  end  of  the  wing.  There 
are  no  traces  of  muscles  or 
elastic  ligaments  in  the  wing 
which  could  aid  in  the  folding. 
Mechanics  of  Flight. — The 
mechanism  of  insect  flight  is 
much  less  complex  than  one 
might  anticipate.  Indeed, 
owing  to  the  structure  of  the 
wing  itself,  simple  up  and 
down  movements  are  suffi- 
cient for  the  simplest  kind  of 
flight.  During  oscillation, 
the  plane  of  the  wing  changes, 
as  may  be  demonstrated  by 
holding  a  detached  wing  by 
its  base  and  blowing  at  right 
angles  to  its  surface ;  the  mem- 
brane of  the  wing  then  yields 
to  the  pressure  of  the  air  while 

the  rigid  anterior  margin  does  not,  to  any  great  extent.  Similarly, 
as  the  wing  moves  downward  the  membrane  is  inclined  upward  by  the 
resistance  of  the  air,  and  as  the  wing  moves  upward  the  membrane 
bends  downward.  Therefore,  by  becoming  deflected,  the  wing  encoun- 
ters a  certain  amount  of  resistance  from  behind,  which  is  sufficient  to 
propel  the  insect.  The  faster  the  wings  vibrate,  the  greater  the  deflec- 
tion, the  greater  the  resistance  from  behind,  and  the  faster  the  flight 
of  the  insect. 

The  path  traced  in  the  air  by  a  rapidly  vibrating  wing  may  be  deter- 
mined by  fastening  a  bit  of  gold  leaf  to  the  tip  of  the  wing  and  allowing 
the  insect — a  wasp,  for  example — to  vibrate  its  wings  in  the  sunlight, 


Fig.  74. — Wing  of  Leptinotarsa  decemlineata.  A, 
spread;  B,  folded;  a,  costal  joint;  ah,  articular  head; 
an,  anterior  system  of  veins;  b,  transverse  vein;  c, 
cotyla;  d,  joint;  in,  middle  system  of  veins;  p,  poste- 
rior system  of  veins. — After  Tower. 


58 


ENTOMOLOGY 


against  a  dark  background.  Under  these  conditions,  the  trajectory 
of  the  wing  appears  as  a  luminous  elongate  figure  8.  During  flight, 
the  trajectory  consists  of  a  continuous  series  of  these  figures,  as  in  Fig. 

75- 

Marey,  an  authority  on  animal  locomotion,  used  chronophotography, 

among  other  methods,  in  studying  the  proc- 
ess of  flight,  and  obtained  at  first  twenty, 
and  later  one  hundred  and  ten,  successive 
photographs  per  second  of  a  bee  in  flight. 
As  the  wings  were  vibrating  190  times  per 
second,  however,  the  images  evidently 
-Trajectory  of  the  wing  represented  isolated  and  not  consecutive 

of  an  insect.  ^ 

phases  of  wing  movement.  Nevertheless, 
the  images  could  be  interpreted  without  difficulty,  in  the  light  of 
the  results  obtained  by  other  methods.     At  length  he  obtained  sharp 


Fig. 


of  a  second. 

The  frequency  of  wing  vibration  may  be  ascertained  from  the  note 
made  by  the  wing— if  it  vibrates  rapidly  enough  to  make  one;  and,  in 


Pig.  76. — Records  of  wing  vibration.  A,  mosquito.  Anopheles.  Above  is  the  wing 
record  and  below  is  the  record  of  a  tuning-fork  which  vibrated  264.6  times  per  second.  B, 
wasp,  Polistes.     The  tuning-fork  in  this  instance  had  a  vibration  frequency  of  97.6. 

any  case,  may  be  determined  graphically  by  means  of  a  kymograph, 
which,  in  one  of  its  forms,  consists  of  a  cylinder  covered  with  smoked 
paper  and  revolved  by  clockwork  at  a  uniform  rate.  The  insect  is 
held  in  such  a  position  that  each  stroke  of  the  wing  makes  a  record  on 
the  smoked  paper,  as  in  Fig.  76,  A.  Comparing  this  record  with  one 
made  on  the  same  paper  by  a  tuning-fork  of  known  vibration  period, 
the  frequency  of  wing  vibration  can  be  determined  with  great  accuracy. 


ANATOMY    AND    PHYSIOLOGY 


59 


As  the  wing  moves  in  the  arc  of  a  circle,  the  radius  of  which  is  the  length 
of  the  wing,  the  extreme  tip  of  the  wing  records  only  a  short  mark;  if, 
however,  the  wing  is  pressed  against  the  smoked  cylinder,  a  large  part 
of  the  figure-8  trajectory  may  be  obtained,  as  in  Fig.  76,  B.  The  wings 
of  the  two  sides  move  synchronously,  as  Marey  found. 

The  smaller  the  wings  are,  the  more  rapidly  they  vibrate.     Thus  a 
butterfly   {P.   rapce)   makes  9 
strokes  per  second,  a  dragon 
fly   28,  a  sphingid  moth  72,  a 
bee  190  and  a  house  fly  330. 

Wing  Muscles. — The  base 
of  a  wing  projects  into  the 
thoracic  cavity  and  serves  for 
the  insertion  of  the  direct 
muscles  of  flight.  Regarding 
the  wing  as  a  lever  (Fig.  77, 
A)  with  the  fulcrum  at  p,  it 
is  easy  to  understand  how  the 
contraction  of  muscle  e  raises 
the  wing  and  that  of  muscle  d 
lowers  it.  These  muscles  are 
shown  diagrammatically  in  Fig. 
77,  B.  Besides  these,  there 
are   certain  muscles  of  flight 

which  act  indirectly  upon   the  ,^'^-  'Z--^-    ^fSra^a   to   illustrate  the  action 

J       ^  of  the  wing  muscles  of  an  insect.     B,  diagram  of 

wings,    by  altering  the  form  of  wing  muscles,     a,   alimentary    canal;   cm.   muscle 

11             .             ,,        rpi          ,1  for  contracting  the  thorax,  to  depress  the  wings; 

tne    tnOraClC    wall.        inUS   trie  ^^    depressor    of    wing;    e,    elevator   of   wing;    ex, 

muscle  id  (Fis    77    B)  elevates  ^^^cle  for  expanding  the  thorax,  to  elevate  the 

wings;  id,  indirect  depressor;  ie,  indirect  elevator; 

the  wing  by  pulling  the  tergum  /.  leg  muscle;  p,   pivot,  or  fulcrum;  s.  sternum;  t, 

toward  the  sternum;  and  the  tergum;  ^g.  wing.-After  Graber. 
longitudinal  muscle  id  depresses  the  wing  indirectly  by  arching  the  ter- 
gum of  the  thorax. 

Though  up  and  down  movements  are  all  that  are  necessary  for  the 
simplest  kind  of  insect  flight,  the  process  becomes  complex  in  proportion 
to  the  efl&ciency  of  the  flight.  Thus  in  dragon  flies  there  are  nine 
muscles  to  each  wing:  five  depressors,  three  elevators  and  one  adductor. 
The  earlier  accounts  of  the  mechanics  of  flight  by  Marey  and  others 
have  been  modified  and  improved  upon  by  Stellwaag  and  by  Ritter, 
whose  modern  methods  of  investigation  have  added  considerably  to  our 
knowledge  of  the  subject.  These  later  authors  have  shown,  particu- 
larly, the  parts  played  by  the  thoracic  sclerites  during  flight. 


6o  ENTOMOLOGY 

The  development  of  aviation  was  due  largely  to  thorough  studies 
of  the  flight  of  birds  and  insects. 

Abdomen. — The  chief  functions  of  the  abdomen  are  respiration  and 
reproduction,  to  which  should  be  added  digestion.  The  abdomen  as  a 
whole  has  undergone  less  differentiation  than  the  thorax  and  presents  a 
simpler  and  more  primitive  segmentation. 

Segments. — A  typical  abdominal  segment  bears  a  dorsal  plate,  or 
tergum  (notum)  and  a  ventral  plate,  or  sternum,  the  two  being  connected 
by  a  pair  of  pleural  membranes,  which  facilitate  the  respiratory  move- 
ments of  the  tergum  and  sternum.  Abdominal  tergites  and  sternites 
are  often  termed  urotergites  and  urosternites,  respectively.  Most  of 
the  abdominal  segments  have  spiracles,  one  on  each  side,  situated  in  or 
near  the  pleural  membranes  of  the  first  seven  or  eight  segments.  The 
total  number  of  pairs  of  spiracles  is  as  follows: 

Thoracic    Abdominal  Total 

Campodea 2  i  3 

Japyx^ 4  7  II 

Machilis 2  7  9 

Lepisma 2  8  10 

Nicoletia. • 2  8  10 

Orthoptera 2  8  10 

Odonata 2  8  10 

Heteroptera 2  6(7)  8(9) 

Lepidoptera 2  7  9 

Diptera 2  7  9 

1  Japyx  actually  has  four  thoracic  and  seven  abdominal  spiracles,  as  described  and 
illustrated  by  Grassi  (1888),  Willem  (1900)  and  Verhoeff  (1904);  a  study  of  their  figures 
indicates,  however,  that  the  spiracles  may  have  migrated  forward,  and  that  the  fourth 
thoracic  pair  (there  being  two  pairs  in  the  metathorax)  belongs  morphologically  to  the 
first  abdominal  segment. 

Number  of  Abdominal  Segments. — Though  only  ten  abdominal 
segments  are  evident  in  many  adult  insects  and  many  larvae  as  well, 
the  typical  number  is  eleven,  and  the  maximum  twelve.  In  embryos  of 
Thysanura,  Orthoptera,  Ephemerida,  Odonata,  Coleoptera  and  Hy- 
menoptera,  eleven  abdominal  neuromeres  (primitive  ganglia)  have  been 
found  by  Heymons  and  others;  each  neuromere  representing  a  segment; 
and  the  twelfth  segment  is  present  as  a  telson,  a  terminal,  segment  con- 
taining the  anus,  but  without  a  neuromere  and  never  bearing  a  pair  of 
appendages.  This  telson  is  present  also  in  the  adults  of  some  generalized 
insects,  as  Orthoptera.  In  the  more  specialized  orders,  ten  may  usually 
be  distinguished,  with  more  or  less  difiiculty,  though  the  number  is 
apparently,  and  in  some  cases  actually,  less  owing  to  modifications  of 


ANATOMY   AND   PHYSIOLOGY 


6l 


the  base  of  the  abdomen  in  relation  to  the  thorax,  but  especially  to 
modifications  of  the  extremity  of  the  abdomen,  for  sexual  purposes. 

Modifications. — In  aculeate  Hymenoptera  the  first  segment  of  the 
abdomen  has  been  transferred  to  the  thorax,  where  it  is  known  as  the 
propodeiim,  or  median  segment;  in  other  words,  what  appears  to  be  the 
first  abdominal  segment  is  actually  the  second;  this,  as  in  bees  and 
wasps,  often  forms  a  petiole,  which  enables 
the  sting  to  be  applied  in  almost  any  direc- 
tion. In  Cynipidae  the  tergum  of  segment 
two  or  three  occupies  most  of  the  abdom- 
inal mass,  the  remaining  segments  being 
reduced  and  inconspicuous.  The  terminal 
segments  of  the  abdomen  often  telescope 
into  one  another,  as  in  many  Coleoptera  and 
Hymenoptera  (Chrysididae),  or  undergo 
other  modifications  of  form  and  position 
which  obscure  the  segmentation.  As  to 
the  number  of  evident  (not  actual)  abdom- 
inal segments,  Coleoptera  show  five  or  six 
ventrally  and  seven  or  eight  dorsally; 
Lepidoptera,  seven  in  the  female  and  eight 
in  the  male;  Diptera,  nine  (male  Tipulidae) 
or  only  four  or  five;  and  Hymenoptera,  nine 
(Tenthredinidas)  or  as  few  as  three  (Chry- 
sididae). In  the  larvae  of  these  insects, 
nine  or  ten  abdominal  segments  are  usually 
distinguishable,  though  the  tenth  is  fre- 
quently   modified,     being     in    caterpillars 

united  with   the  ninth.  Fig.    78.— Ventral  aspect  of  the 

.  J  -nv      !•  1    1         •       1    abdomen    of    a    female    Machilis 

Appendages.— Rudimentary  abdommal  maritima,  to  show  rudimentary 
limbs  occur  in  Thysanura    {Machilis,  Fig.   (^h^e^SJ  apSSeVf'^tL*^^^^^^ 

78).     Functional  abdominallegS  do  not  occur    segment  is  omitted.)    c,  c,  c,  lateral 
11,      •  iT_j.*i  ^1.         1.J  cerci  and  median  pseudocercus. — 

m  adult  msects,  but  m  larvae  the  abdom-  p^^^^  qudemans. 
inal    rolegs    (Fig.     66)     are     homologous 

with  the  thoracic  legs  and  the  other  paired  segmental  appendages,  as 
the  embryology  shows.  The  embryo  of  (Ecanthus,  according  to  Ayers, 
has  ten  pairs  of  abdominal  appendages  (Fig.  199),  equivalent  to  the 
thoracic  legs.  Most  of  these  embryonic  abdominal  appendages  are 
only  transitory,  but  the  last  three  pairs  frequently  persist  to  form  the 
genitalia,  as  in  Orthoptera  (to  which  order  (Ecanthus  belongs).     In 


62  ENTOMOLOGY 

Collembola,  the  embryo  has  paired  abdominal  limbs,  and  those  of  the 
first  abdominal  segment  eventually  unite  to  form  the  peculiar  ventral 
tube  (Fig.  13)  of  these  insects,  while  those  of  the  fourth  segment  form 
the  characteristic  leaping  organ,  or  fur cula,  and  those  of  the  third,  the 
tenaculum. 

Cerci. — In  many  of  the  more  generalized  insects  the  abdomen  bears 
at  its  extremity  a  pair  of  appendages  termed  cerci.  These  occur  in 
both  sexes  and  are  frequently  long  and  multiarticulate,  as  in  Thysanura 
(Figs.  78,  10,  11),  Plecoptera  (Fig.  19)  and  Ephemerida  (Figs.  20,  B;S6) 
though  shorter  in  cockroaches  and  reduced  to  a  single  sclerite  in  Locus- 
tidae  (Fig.  89).  The  paired  cerci,  or  cercopoda  of  Packard,  are  usually 
though  not  always  associated  with  the  eleventh  abdominal  segment  and 
are  homologous  with  legs,  as  Ayers  has  found  in  (Ecanthus  and  Wheeler 
in  Xiphidium.  As  to  their  function,  the  cerci  of  Thysanura  are  tactile, 
and  those  of  the  cockroach  olfactory,  while  the  cerci  of  male  Locustidae 
often  serve  to  hold  the  female  during  copulation. 

The  so-called  "median  cercus"  or  "filum  terminale"  of  Thysanura 
(Figs.  II,  78)  and  Ephemerida  (Fig.  86)  resembles  the  true  cerci  of 
these  insects  in  being  multiarticulate  and  usually  long,  and  in  having  the 
same  function;  but  differs  from  these  morphologically  in  arising  as  a 
median  dorsal  prolongation  of  the  eleventh  abdominal  segment;  being 
therefore  not  equivalent  to  one  of  the  paired  segmental  appendages. 
For  this  median  filament  the  term  pseudocercus  is  appropriate. 

Extremity  of  Abdomen. — Various  modifications  of  the  terminal 
segments  of  the  abdomen  occur  for  the  purposes  of  defecation  and 
especially  reproduction.  The  anus,  dorsal  in  position,  opens  always 
through  the  last  segment  and  is  often  shielded  above  by  a  suranal  plate 
and  on  each  side  by  a  lateral  plate.  The  genital  orifice  is  always  ventral 
in  position  and  occurs  commonly  on  the  ninth  abdominal  segment, 
though  there  is  some  variation  in  this  respect.  The  external,  or 
accessory,  organs  of  reproduction  are  termed  the  genitalia. 

Female  Genitalia. — In  Neuroptera,  Coleoptera,  Lepidoptera  and 
Diptera  the  vagina  simply  opens  to  the  exterior  or  else  with  the  anus 
into  a  common  chamber,  or  cloaca.  Often,  as  in  Cerambyx  (Fig.  79) 
and  Dasyneura  (Fig.  80)  the  attenuated  distal  segments  of  the  abdomen 
serve  the  purpose  of  an  ovipositor;  thus  in  Itonididae,  the  terminal 
segments,  telescoped  into  one  another  when  not  in  use,  form  when 
extruded  a  lash-like  organ  exceeding  frequently  the  remainder  of  the 
body  in  length. 

A  true  ovipositor  occurs  in  Thysanura,  Orthoptera,  Odonata,  Hemip- 


ANATOMY    AND    PHYSIOLOGY 


63 


tera,  Hymenoptera  and  some  other  orders  of  insects.  The  ovipositor 
consists  essentially  of  three  pairs  of  valves,  or  gonapophyses — a  dorsal,  a 
ventral  and  an  inner  pair.  The  two  inner  valves  form  a  channel  through 
which  the  eggs  are  conveyed.  In  Tettigoniidai  (Fig.  81)  the  three 
J       ^       5       ^  valves  of  each  side  are  held  to- 

gether by  tongues  and  grooves, 
which,  however,  permit  sliding 


Fig.  79. — Abdomen  of  female  beetle,  Cer- 
ambyx,  in  which  the  last  three  segments  are 
used  as  an  ovipositor. — After  Kolbe. 


Fig.  80. — Abdomen  of  a  female  midge, 
Dasyneura  leguminicola,  to  show  the 
pseudo -ovipositor. 


movements  to  take  place.  Most  authorities  have  found  that  the 
gonapophyses  belong  to  the  segmental  series  of  paired  appendages — 
are  homodynamous  with  limbs — and  pertain  commonly  to  abdominal 


Fig.  81. — Ovipositor  of  Phasgonura. — A,  lateral  aspect;  B,  ventral  aspect;  C,  transverse 
section;  c,  cerci;  d,  dorsal  valve;  i,  inner  valve;  v,  ventral  valve.  The  numbers  refer  to  ab- 
dominal segments. — After  Kolbe  and  Dewitz. 

segments  eight,   nine    and   ten;   though    there  are  different  views  in 
regard  to  this. 

The  ovipositor  attains  its  greatest  complexity  in  Hymenoptera,  in 
which  it  becomes  modified  for  sawing,  boring  or  stinging.     In  Sirex  (Fig. 


64 


ENTOMOLOGY 


82)  the  inner  valves  are  united;  in  Apis  the  dorsal  valves  are  represented 
by  a  pair  of  palpi,  the  inner  valves  unite  to  form  the  sheath  (Fig.  83,  B), 
and  the  ventral  two  form  the  darts,  each  of  which  has  ten  barbed  teeth 
behind  its  apex,  which  tend  to  prevent  the  with- 
drawal of  the  sting  from  a  wound.  The  action  of 
the  sting,  as  described  by  Cheshire,  is  rather  com- 
plex. Briefly,  the  sheath  serves  to  open  a  wound 
and  to  guide  the  darts;  these  strike  in  alternately, 
interrupted  at  intervals  by  the  deeper  plunging  of 
the  sheath  (Fig.  83,  A).  The  poison  of  the  honey 
bee  is  secreted  by  two  glands,  one  acid  and  the 
other  alkaline.  The  former  (Fig.  84)  consists  of  a 
glandular  region  which  secretes  formic  acid,  of  a 
reservoir,  and  a  duct  that  empties  its  contents  into 
the  channel  of  the  sheath.  The  alkaline  gland  also  opens  into  the  reser- 
voir. It  is  said  that  both  fluids  are  necessary  for  a  deadly  effect;  and 
that  in  insects  which  simply  paralyze  their 
prey,  as  the  solitary  wasps,  the  alkaline 
glands  are  functionless. 


Fig.  82. — Cross-sec- 
tion of  the  ovipositor  of 
Sir  ex.  c,  channel;  d, 
d,  dorsal  valves;  i, 
united  inner  valves;  v, 
V,  ventral  valves.— After 
Taschenberg 


Fig.  83. — Sting  of  honey  bee.  A,  i,  2,  3,  posi- 
tions in  three  successive  thrusts;  s,  sheath.  B, 
cross-section;  c,  channel;  i,  united  inner  valves, 
forming  the  sheath;  v,  v,  ventral  valves,  or  darts. — 
A,  after  Cheshire;  B,  after  Penger. 


Fig.  84. — Sting  and  poison  appara- 
tus of  honey  bee.  ag,  accessory  gland ; 
p,  palpus;  pg,  poison  gland  (formic 
acid);  r.  reservoir;  s,  sting. — After 
Kraepelin. 


Male  Genitalia. — The  penis  may  be  hollow  or  else  solid,  and  in  the 
latter  case  the  contents  of  the  ejaculatory  duct  are  spread  upon  its 
surface.  Morphologically,  the  male  gonapophyses  correspond  to  those 
of  the  female.  The  penis  (Fig.  85)  represents  the  two  inner  valves  of 
the  ovipositor  and  is  frequently  enclosed  by  one  or  two  pairs  of  valves. 


ANATOMY   AND  PHYSIOLOGY 


6S 


In  Ephemerida  the  two  inner  valves  are  partly  or  entirely  separate 
from  each  other,  forming  two  intromittent  organs  (Fig.  86) . 

In  male  Odonata,  the  ejaculatory  duct  opens  on  the  ninth  abdominal 
segment,  but  the  copulatory  organ  is  placed  on  the  under  side  of  the  sec- 
ond segment,  to  which  the  spermatozoa  are  transferred  by  the  bending 
of  the  abdomen.  At  copulation,  the  abdominal  claspers  of  the  male 
grasp  the  neck  of  the  female,  and  the  latter  bends  her  abdomen  forward 
until  the  tip  reaches  the  pecuHar  copulatory  apparatus  of  the  male. 

The  claspers  of  the  male  consist  of  a  single  pair,  variously  formed. 
They  are  present  in  Ephemerida,  Neuroptera,  Trichoptera,  Lepidoptera 
(Fig.  87),  Diptera  and  some  Hymenoptera,  though  not  in  Coleoptera, 
and  often  afford  good  specific  characters,  as  in  Odonata.  In  butterflies 
of  the  genus  Thanaos,  the  claspers  are  pecuHar  in  being  strongly 
asymmetrical.  In  Odonata  (Fig.  88,  A)  and  Orthoptera  (Fig.  89,  A) 
the  superior  appendages  of  the  male  often  serve  as  claspers. 

In  many  insects  the  tergum  of  the  last  abdominal  segment  forms  a 
small  suranal  plate  (Fig.  89,  B,  sp);  this  sometimes  supplements  the 
claspers  of  the  male  in  their  function,  as  in  Lepidoptera  (Fig.  87,  A,  s). 

2.  Integument 

Insects  excel  all  other  animals  in  respect  to  adaptive  modifications  of 
the  integument.     No  longer  a  simple  limiting  membrane,  the  integu- 


FiG.  85. — Extremity  of  abdomen  of  a 
male  beetle,  Hydrophilus,  ventral  aspect,  g, 
genitalia;  p,  penis;  v^,  v',  pairs  of  valves 
enclosing  the  penis;  6-9,  sterna  of  abdominal 
segments. — Aiter  Kolbe. 


'■■-.A^ 

1: 

H 

1 

c 

\ 

c  M 

\\  ^ 

m 

B 

Fig.  86. — Extremity  of  abdomen  of  a 
male  May  fly,  Hexagenia  variabilis,  ventral 
aspect,  c,  c,  c,  cerci  and  pseudocercus  (medi- 
an); cl,  cl,  claspers;  i,  i,  intromittent  organs. 


ment  has  become  hardened  into  an  external  skeleton,  evaginated  to 
form   manifold   adaptive  structures,  such  as  hairs  and  scales,  and 


66 


ENTOMOLOGY 


invaginated,  along  with  the  underlying  cellular  layer,  to  make  glands  of 
various  kinds. 

Chitin. — The  skin,  or  cuticula,^  of  an  insect  differs  from  that  of  a 
worm,  for  example,  in  being  thoroughly  permeated  with  a  pecuHar  sub- 
stance known  as  chitin — the  basis  of  the  arthropod  skeleton.     This  is  a 


Fig.  87. — Genitalia  of  a  moth,  Samia  cecropia.  A,  male;  B,  female;  a,  anus;  c,  c, 
claspers;  o,  opening  of  common  oviduct;  p,  penis;  5,  uncus  (the  doubly  hooked  organ); 
V,  vestibule,  into  which  the  vagina  opens.     The  numbers  refer  to  abdominal  segments. 

substance  of  remarkable  stability,  for  it  is  unaffected  by  almost  all  ordi- 
nary acids  and  alkalies,  though  it  is  soluble  in  sodic  or  potassic  hypo- 
chlorite (respectively,  Eau  de  Labarraque  and  Eau  de  Javelle)  and 
yields  to  boihng  sulphuric  acid.     If  kept  for  a  year  or  so  under  water, 


Pig.  88. — Terminal  abdominal  appendages  of  a  dragon  fly,  Plathemis  tri?naculala.  A, 
male;  B.  female,  i,  inferior  appendage;  5,  s,  superior  appendages.  The  numbers  refer  to 
abdominal  segments. 

however,  chitin  undergoes  a  slow  dissolution,  possibly  a  putrefaction, 
which  accounts  in  a  measure  for  the  rapid  disappearance  of  insect 
skeletons  in  the  soil  (Miall  and  Denny).  By  boiling  the  skin  of  an 
insect  in  potassic  hydroxide  it  is  possible  to  dissolve  away  the  cuticular 
framework,  leaving  fairly  pure  chitin,  without  destroying  the  organized 

1  The  cuticula  of  an  insect  should  be  distinguished  from  the  cuticle  of  a  vertebrate,  the 
former  being  a  hardened  fluid,  while  the  latter  consists  of  cells  themselves,  in  a  dead  and 
flattened  condition. 


ANATOMY    AND    PHYSIOLOGY 


67 


form  of  the  integument,  though  less  than  half  the  weight  of  the  integu- 
ment is  due  to  chitin.  The  formula  of  chitin  is  given  as  CgHuNOa  or 
C18H15NO12  by  Krukenberg,  and  many  adopt  the  formula  C15H26N2O10; 
though  no  two  chemists  agree  as  to  the  exact  proportions  of  these 
elements,  owing  probably  to  variations  in  the  substance  itself  in  differ- 


89  10  11 


Fig.  89. — Extremity  of  the  abdomen  of  a  grasshopper,  Melanoplns  differenlialis.  A, 
male-  B,  female.  The  terga  and  sterna  are  numbered,  c,  cercus;  d,  dorsal  valves  of  ovi- 
positor; e,  egg  guide;  p,  podical  plate;  s,  spiracle;  sp,  suranal  plate;  v.  ventral  valves  of 
ovipositor. 

ent  insects  or  even  in  the  same  species  of  insect.     Iron,  manganese  and 
certain  pigments  also  enter  into  the  composition  of  the  integument. 

Chitin  is  not  peculiar  to  arthropods,  for  it  has  been  detected  in  the 
set£e  and  pharyngeal  teeth  of  annelid  worms,  the  shell  of  Lingula  and  the 
pen  of  the  cuttle  fish  (Krukenberg) . 

The  chitinous  integument  (Fig.  90)  of  most  insects  consists  of  two 
layers:  (i)  an  outer  layer,  homogeneous,  dense, 
without  lamellae  or  pore  canals,  and  being  the 
seat  of  the  cuticular  colors;  (2)  an  inner  layer, 
"thickly  pierced  with  pore  canals,  and  always 
in  layers  of  different  refractive  indices  and  differ- 
ent stainability."  (Tower.)  These  two  layers, 
respectively  primary  and  secondary  cuticula,  are 
radically  different  in  chemical  and  physical  prop- 
erties. 

from  the  hypodermis  cells,  the  primary  cuticula  ^X^cutic™!!'*:^":: 
being  the  first  to  form  and  harden.  dermis  cell;  n,  nucleus.' — 

The  fluid  that  separates  the  old  from  the  new  ^^*"  Tower. 
cuticula  at  ecdysis  is  poured  over  the  hypodermis  by  certain  large  special 
cells,  which,  according  to  Tower,  "are  not  true  glands,  but  the  setiger- 
ous  cells  which,  in  early  Hfe,  are  chiefly  concerned  with  the  formation 
of  the  hairs  upon  the  body;  but  upon  the  loss  of  these,  the  cell  takes 
on  the  function  of  secreting  the  exuvial  fluid,  which  is  most  copious  at 


Fig.    90.  —  Section 
through   integument    of   a 
^      ,      ,  .  n    •!  -•  beetle,     Chrysobothris.      b. 

Each    layer    arises    as     a  fluid    secretion    basement     membrane;    cK 


68 


ENTOMOLOGY 


pupation.     These  cells  degenerate  in  the  pupa,  and  take  no  part  in  the 
formation  of  the  imaginal  ornamentation." 


\ 


Fig.  91. — Modifications  of  the  hairs  of  bees.     A,  B,  Megachile;  C,  E,  F,  Colletes;  D,  Chelos' 

toma. — After  Saunders. 
I 

Histology. — The  chitinous  cuticula  owes  its  existence  to  the  activity 
of  the  underlying  layer  of  hypodermis  cells  (Fig.  90),  a  single  layer, 


Pig.  92. — Section  of  antenna  of  a  moth, 
Salurnia,  to  show  developing  hairs,  c,  cutic- 
ula; /,  formative  cell,  or  trichogen,  of  hair; 
h,  hypodermis;  t,  trachea. — After  Semper. 


Fig.  93. — Radial  section  through  the 
base  of  a  hair  of  a  caterpillar,  Pieris  rapce. 
c,  cuticula;  /,  formative  cell,  or  trichogen; 
h,  hair;  hy,  hypodermis. 


Ectodermal  in  origin.  These  cells,  distinct  in  embryonic  and  often  in 
early  larval  life,  subsequently  become  confluent  by  the  disappearance 
6i  the  intervening  cell  walls,  though  each  cell  is  still  indicated  by  its 


ANATOMY   AND   PHYSIOLOGY 


69C 


nucleus.  The  cells  are  limited  outwardly  by  the  cuticula  and  inwardly, 
by  a  delicate,  hyaline  basement  membrane;  they  contain  pigment  granules,' 
fat-drops,  etc. 

Externally  the  cuticula  may  be  smooth,  wrinkled,  striate,  granulate,: 
tuberculate,  or  sculptured  in  numberless  other  ways;  it  may  be  shaped 
into  all  manner  of  structures,  some  of  which  are  clearly  adaptive,  while 
others  are  unintelligible. 

Hairs,  Setae  and  Spines. — These  occur  universally,  serving  a  great 
variety  of  purposes;  they  are  not  always  simple  in  form,  but  are  often 
toothed,  branched  or  otherwise  modified 
(Fig.  91) .  Hairs  and  bristles  are  frequently 
tactile  in  function,  over  the  general  integu- 
ment or  else  locally;  or  olfactory,  as  on  the 
antennae  of  moths;  or  occasionally  auditory, 
as  on  the  antennae  of  the  male  mosquito; 
these  and  other  sensory  modifications  are 
described  beyond.  The  hairy  clothing  of 
some  hibernating  caterpillars  (as  Isia  isa- 
bella)  probably  protects  them  from  sudden 
changes  of  temperature.  Hairs  and  spines 
frequently  protect  an  insect  from  its  enemies, 
especially  when  these  structures  are  glandu- 
lar and  emit  a  malodorous,  nauseous  or 
irritant  fluid.  Glandular  hairs  on  the  pul- 
villi  of  many  flies,  beetles,  etc.,  enable  these 
insects  to  walk  on  slippery  surfaces.  The 
twisted  or  branched  hairs  of  bees  serve  to 

.  1111  11  •  •         1        ^  ^J^-    94-— Vanous     forms    of 

gather   and  hold   pollen  grams;  m  short,  scales.    A,E,thysa.nnTan,Machi- 
these  simple  structures  exhibit  a  surprising  ^;^:^SJ::^X:SXi^c^S. 
variety  of  adaptive  modifications,  many  of 
which  will  be  described  in  connection  with  other  subjects. 

A  hair  arises  from  a  modified  hypodermis  cell,  formative  cell  or 
trichogen  (Fig.  92),  the  contents  of  which  extend  through  a  pore  canal 
into  the  interior  of  the  hair  (Fig.  93) ;  sometimes,  to  be  sure,  as  in 
glandular  or  sensory  hairs,  the  hair  cell  is  multinucleate,  representing, 
therefore,  as  many  cells  as  there  are  nuclei.  The  wall  of  a  hair  is 
continuous  with  the  general  cuticula  and  at  moulting  each  hair  is 
stripped  off  with  the  rest  of  the  cuticula,  leaving  in  its  place  a  new  hair, 
which  has  been  forming  inside  the  old  one. 

Scales. — Besides  occurring  throughout  the  order  Lepidoptera  and 
in  numerous  Trichoptera,  scales  are  found  in  many  Thysanura  and 


70 


ENTOMOLOGY 


Fig.    95. — Cross-section    of    scale 
Anosia. — After  Mayer. 


Collembola,  several  families  of  Coleoptera  (including  Dermestidae, 
Cerambycidae  and  Curculionidae) ,  a  few  Diptera  and  a  few  Psocidae. 

Though  diverse  in  form  (Fig.  94) ,  scales  are  essentially  flattened  sacs 
having  at  one  end  a  short  pedicel  for  attachment  to  the  integument. 
The  scales  usually  bear  markings,  which  are  more  or  less  characteristic 

of  the  species;  these  markings,  always 
minute,  are  in  some  species  so  exqui- 
sitely fine  as  to  test  the  highest  powers 
of  the  microscope;  the  scales  of  certain 
Collembola  {Lepidocyrtus,  etc.)  have  long 
been  used,  under  the  name  of  "  Podura  "  scales,  to  test  the  resolving  power 
of  objectives,  for  which  purpose  they  are  excelled  only  by  some  of  the 
diatoms.  Butterfly  scales  are  marked  with  parallel  longitudinal 
ridges  (Fig.  94,  C),  which  are  confined  almost  entirely  to  the  upper,  or 
exposed,  surface  of  the  scale  (Fig.  95)  and  number  from  33  or  less 
(Anosia)  to  1,400  {Morpho)  to  each  scale,  the  striae  being  in  the  latter 
genus  from  .002  mm.  to  .0007  mm. 

apart  (Kellogg) ;  between  these  longi-  ^       ^       ^    ( 

tudinal  ridges  may  be  discerned 
delicate  transverse  markings.  Inter- 
nally, scales  are  hollow  and  often 
contain  pigments  derived  from  the 
blood. 

On  the  wing  of  a  butterfly  the 
scales  are  arranged  in  regular  rows  and 
overlap  one  another,  as  in  Fig.  96 ;  in 
the  more  primitive  moths  and  in  Tri- 
choptera,  however,  their  distribution 
is  rather  irregular. 

A  scale  is  the  equivalent  of  a  hair, 

for  (l)  a  complete  series  of  transitions  ^^^-  96.— Arrangement  of  scales  on  the 
-  ,     .  ,       ,  wing  of  a  butterfly,  Papilio. 

from  hairs  to  scales  may  be  found  on 

a  single  individual  (Fig.  97) ;  and  (2)  hairs  and  scales  agree  in  their  man- 
ner of  development,  as  shown  by  Semper,  Schaffer,  Spuler,  Mayer  and 
others.  Both  hairs  and  scales  arise  as  processes  from  enlarged  hypo- 
dermis  cells,  or  formative  cells  (Fig.  98).  The  scale  at  first  contains 
protoplasm,  which  gradually  withdraws,  leaving  short  chitinous  strands 
to  hold  the  two  membranes  of  the  scale  together. 

Uses  of  Scales. — Among  Thysanura  and  Collembola,  scales  occur 
only  on  such  species  as  live  in  comparatively  dry  situations,  from  which 


ANATOMY   AND   PHYSIOLOGY 


71 


it  may  be  inferred  that  the  scales  serve  to  retard  the  evaporation  of  mois- 
ture through  the  delicate  integument  of  these  insects.     This  inference  is 


Fig.  97. — Hairs  and  scales  of  a  moth,  Samia  cecropia. 

supported  by  the  fact  that  none  of  the  scaleless  Collembola  can  live  long 
in  a  dry  atmosphere;  they  soon  shrivel  and  die  even  under  conditions 


Fig.  98. — Development  of  butterfly  scales.  FiG.  99. — Androconia     of     butterflies.     A, 
A.  Vanessa;  B,  Anosia.     6,  basement  mem-  Pieris  rapm;  B,    Everes  comyntas. 

brane;  /,  formative  cell;  h,  hypodermis;  s, 
scale. — After  Mayer. 

of  dryness  which  the  scaled  species  are  able  to  withstand.     In  Lepidop- 
tera  the  scales  are  possibly  of  some  value  as  a  mechanical  protection; 


72 


ENTOMOLOGY 


they  have  no  injfluence  upon  flight,  as  Mayer  has  proved,  and  appear  to 
be  useful  chiefly  as  a  basis  for  the  development  of  color  and  color 
patterns — which  are  not  infrequently  adaptive. 

Androconia. — The  males  of  many  butterflies,  and  the  males  only, 
have  peculiarly  shaped  scales  known  as  androconia  (Fig.  99) ;  these  are 
commonly  confined  to  the  upper  surfaces  of  the  front  wings,  where  they 
are  mingled  with  the  ordinary  scales  or  else  are  disposed  in  special 
patches  or  under  a  fold  of  the  costal  margin  of  the  wing  (Thanaos). 
The  characteristic  odors  of  male  butterflies  have  long  been  attributed 
to  these  androconia,  and  M.  B.  Thomas  has  found  that  the  scales  arise 


Fig.  100. — Section  across  tarsus  of  a  beetle, 
Hylobius,  to  show  bulbous  glandular  hairs. — 

After  SiMMERMACHER. 


Fig.  ioi. — Stinging  hair  of  a  caterpillar, 
Gaslropacha.  c,  cuticula;  g,  gland  cell;  h, 
hair;  hy,  hypodermis. — After  Claus. 


from  glandular  cells,  which  doubtless  secrete  a  fluid  that  emanates 
from  the  scale  as  an  odorous  vapor,  the  evaporation  of  the  fluid  being 
facilitated  by  the  spreading  or  branching  form  of  the  androconium. 
Similar  scales  occur  also  on  the  wings  of  various  moths  and  some 
Trichoptera  {Mystacides) . 

Glands. — A  great  many  glands  of  various  form  and  function  have 
been  found  in  insects.  Most  of  these,  being  formed  from  the  hypoder- 
mis, may  logically  be  considered  here,  excepting  some  which  are  inti- 
mately concerned  with  digestion  or  reproduction. 

Glandular  Hairs  and  Spines. — The  presence  of  adhesive  hairs  on 
the  empodium  of  the  foot  of  a  fly  enables  the  insect  to  walk  on  a  smooth 
surface  and  to  walk  upside  down;  these  tenent  hairs  emit  a  transparent 
sticky  fluid  through  minute  pore  canals  in  their  apices.  The  tenent 
hairs  of  Hylobius  (Fig.  100)  are  each  supplied  with  a  flask-shaped  unicel- 
lular gland,  the  glutinous  secretion  of  which  issues  from  the  bulbous 


ANATOMY    AND    PHYSIOLOGY  73 

extremity  of  the  hair.     Bulbous  tenent  hairs  occur  also  on  the  tarsi  of 
Collembola,  Aphididas  and  other  insects. 

Nettling  hairs  or  spines  clothe  the  caterpillars  of  certain  Saturniida) 
{Automeris),  Liparidae,  etc.  These  spines  (Fig.  loi),  which  are  sharp, 
brittle  and  filled  with  poison,  break  to  pieces  when  the  insect  is  handled 
and  cause  a  cutaneous  irritation  much  like  that  made  by  nettles.  In 
Lagoa  crispata  (Fig.  102)  the  irritating  fluid 'is  secreted,  as  is  usual,  by 
several  large  hypodermal  cells  at  the  base  of  each  spine.  These  irritating 
hairs  protect  their  possessors  from  almost  all  birds  except  cuckoos. 

Repellent  Glands. — The  various  offensive  fluids  emitted  by  insects 
are  also  a  highly  effective  means  of  defense  against  birds  and  other  in- 
sectivorous vertebrates  as  well  as  against  predace- 
ous  insects.  The  blood  itself  serves  as  a  repellent 
fluid  in  the  oil-beetles  (Meloidae)  and  Coccinellidae, 
issuing  as  a  yellow  fluid  from  a  pore  at  the  end  of 
the  femur.  The  blood  of  Meloidae  (one  species  of 
which  is  still  used  medicinally  under  the  name  of 
''Spanish  Fly")  contains  cantharidine,  an  extremely 
caustic  substance,  which  is  an  almost  perfect  pro- 
tection against  birds,  reptiles  and  predaceous  insects. 
Coccinellidae  and  Lampyridae  are  similarly  exempt  from 
attack.  Larvae  of  Cimbex  when  disturbed  squirt 
jets  of  a  watery  fluid  from  glands  opening  above  the  Fig.  102.— sting- 
spiracles.  Many  Carabid^  eject  a  pungent  and  often  ':^:!Z^:S^_ 
corrosive  fluid  from  a  pair  of  anal  glands  (Fig.  —After  Packard. 
148);  this  fluid  in  Brachinus,  and  occasionally 
in  Galerita  janus  and  a  few  other  carabids,  volatilizes  explosively 
upon  contact  with  the  air.  When  one  of  these  ''bombardier-beetles" 
is  molested  it  discharges  a  puff  of  vapor,  accompanied  by  a  distinct 
report,  reminding  one  of  a  miniature  cannon,  and  this  performance 
may  be  repeated  several  times  in  rapid  succession;  the  vapor  is  acid  and 
corrosive,  staining  the  human  skin  a  rust-red  color.  Individuals  of  a 
large  South  American  Brachinus  when  seized  "immediately  began  to 
play  off  their  artillery,  burning  and  staining  the  flesh  to  such  a  degree 
that  only  a  few  specimens  could  be  captured  with  the  naked  hand, 
leaving  a  mark  which  remained  for  a  considerable  time."     (Westwood.) 

As  malodorous  insects,  Hemiptera  are  notorious,  though  not  a  few 
hemipterous  odors  are  (apart  from  their  associations)  rather  agreeable 
to  the  human  olfactory  sense.  Commonly  the  odor  is  due  to  a  fluid 
frorfi  a  mesothoracic  gland  or  glands,  opening  between  the  hind  coxae. 


74 


ENTOMOLOGY 


Eversible  hypodermal  glands  of  many  kinds  are  common  in  larvae  of 
Coleoptera  and  Lepidoptera.  The  larvae  of  Lina  lap_ponica,  among 
other  Chrysomelidae,  evert  numerous  paired  vesicles  which  emit  a 
peculiar  odor.  The  caterpillars  of  our  Papilio  butterflies,  upon  being 
irritated,  evert  from  the  prothorax  a  yellow  Y-shaped  osmeterium  (Fig. 


0  <■: 


Pig.    103. — Osmeterium    of    Papilio      Pig.  104.— Ventralaspectofworke^honeybee,show- 
/)oZy«:en«.  ing  the  four  pairs  of  wax  scales. — After  Cheshire. 

103)  which  diffuses  a  characteristic  but  indescribable  odor  that  is 
probably  repellent.  The  larva  of  Cerura  everts  from  the  under  side  of 
the  neck  a  curious  spraying  apparatus  which  discharges  formic  acid. 

^  Alluring  Glands.^Odors  are 

'■•         '  largely   used    among   insects   to 

attract  the  opposite  sex.  The 
androconia  of  male  butterflies 
have  already  been  spoken  of. 
Males  of  Catocala  concumhens  dis- 
seminate an  alluring  odor  from 
scent  tufts  on  the  middle  legs. 
Female  saturniid  moths  (as  cecro- 
pia  and  promethea)  entice  the 
males  by  means  of  a  characteris- 
tic odor  emanating  from  the  ex- 
tremity of  the  abdomen.  In 
lycaenid  caterpillars,  an  eversible 
sac  on  the  dorsum  of  the  seventh  abdominal  segment  secretes  a  sweet 
fluid,  for  the  sake  of  which  these  larvae  are  sought  out  by  ants. 

Wax  Glands. — Wax  is  secreted  by  insects  of  several  orders,  but  es- 
pecially Hymenoptera  and  Hemiptera.  In  the  worker  honey  bee  the 
wax  exudes  from  unicellular  hypodermal  glands  and  appears  on  the 


Fig.  105. — Head  of  caterpillar  of  Samia 
cecropia.  a,  antenna;  c,  clypeus;  I,  labrum; 
Ip,  labial  palpus;  m,  mandible;  mp,  maxillary 
palpi;  o,  ocelli;  s,  spinneret. 


ANATOMY    AND    PHYSIOLOGY  75 

under  side  of  the  abdomen  as  four  pairs  of  wax  scales  (Fig.  104),  on 
the  last  four  of  the  six  evident  segments  of  the  abdomen  (Dreyling). 
Plant  lice  of  the  genus  Schizoneura  owe  their  woolly  appearance  to  dense 
white  filaments  of  wax,  which  arise  from  glandular  hypodermal  cells. 
In  scale  insects,  waxen  threads,  emerging  from  cuticular  pores,  become 
matted  together  to  form  a  continuous  shield  over  and  often  under  the 
insect  itself,  the  cast  skins  often  being  incorporated  into  this  waxen 
scale.  The  wax  glands  in  Coccidae  are  simply  enlarged  hypodermis 
cells. 

Some  coccids  produce  wax  in  quantities  sufficient  for  commercial 
use.  Thus  species  of  Ceroplastes  (and  certain  fulgorids  as  well)  in 
India  and  China  yield  a  white  wax  that  is  used  for  making  candles  and 
for  other  purposes. 

The  lac-insect,  Tachardia  lacca,  of  India,  a  scale  insect  Uving  on 
more  than  ninety  species  of  trees  and  shrubs  {Acacia,  Ficus,  Zizyphus, 
etc.),  furnishes  the  lac  from  which  shellac,  lacquer  and  other  varnishes 
are  made.  The  raw  lac  is  the  scale,  or  shell,  of  the  female  insect  (the 
male  producing  scarcely  any  lac)  and  consists  of  a  yellow  to  reddish 
brown  resinous  exudation  containing  considerable  wax,  along  with  the 
cast  skins  of  the  insect.  From  this  material  the  commercial  products 
are  extracted. 

Silk  Glands.^Larvae  of  very  diverse  orders  spin  silk,  for  the  purpose 
of  making  cocoons,  webs,  cases,  and  supports  of  one  kind  or  another. 
Silk  glands,  though  most  characteristic  of  Lepidoptera  and  Trichoptera, 
oceur  also  in  the  cocoon-spinning  larvae  of  not  a  few  Hymenoptera 
(saw  flies,  ichneumons,  wasps,  bees,  etc.),  in  Diptera  (Itonididae), 
Siphonaptera,  Neuroptera  (Chrysopidae,  Myrmeleonidae) ,  and  in 
various  larvae  whose  pupae  are  suspended  from  a  silken  support,  as  in 
the  coleopterous  families  Coccinelhdae  and  Chrysomelidae  (in  part) 
and  the  dipterous  family  Syrphidae,  as  well  as  most  diurnal  Lepidoptera. 

The  silk  glands  of  caterpillars  are  homologous  with  the  true  saHvary 
glands  of  other  insects,  opening  as  usual  through  the  hypopharynx, 
which  is  modified  to  form  a  spinning  organ,  or  spinneret  (Fig.  105). 
The  silk  glands  of  Lepidoptera  are  a  pair  of  long  tubes,  one  on  each  side 
of  the  body,  but  often  much  longer  than  the  body  and  consequently 
convoluted.  Thus  in  the  silk  worm  {Bomhyx  mori)  they  are  from  four 
to  five  times  as  long  as  the  body  and  in  Telea  polyphemus,  seven  times 
as  long.  In  the  silk  worm  the  convoluted  glandular  portion  of  each 
tube  (Fig.  106)  opens  into  a  dilatation,  or  silk  reservoir,  which  in  turn 
empties  into  a  slender  duct,  and  the  two  ducts  join  into  a  short  common 


7-6 


ENTOMOLOGY 


duct,  which  passes  through  the  tubular  spinneret.  Two  divisions  of 
the  spinning  tube  are  distinguished:  (i)  a  posterior  muscular  portion,  or 
thread-press  and  (2)  an  anterior  directing  tube.  The  thread-press  com- 
bines the  two  streams  of  silk  fluid  into  one,  determines  the  form  of  the 
silken  thread  and  arrests  the  emission  of  the  thread  at  times,  besides 
having  other  functions.  The  silk  fluid  hardens  rapidly  upon  exposure 
to  the  air;  about  fifty  per  cent,  of  the  fluid 
is  actual  silk  substance  and  the  remainder 
consists  of  protoplasm  and  gum,  with  traces 
of  wax,  pigment,  fat  and  resin. 


(  Fig.  106. — Silk  glands  of  the 
silk  worm,  Bombyx  mori.  cd, 
common  duct;  d,  one  of  the 
paired  ducts;  g,  g,  Filippi's 
glands;  gl,  gland  proper;  p, 
thread  press;  r,  reservoir. 


Fig.  107. — Sections  of  silk  gland  of  the  silk  worm. 
A,  radial;  B,  transverse,  b,  basement  membrane;  i, 
intima;  5,  glandular  cell  with  branched  nucleus. — 
After  Helm. 


A  transverse  or  radial  section  of  a  silk  gland  shows  a  layer  of  glandu- 
lar epithehal  cells,  with  the  usual  intima  and  basement  membrane  (Fig. 
107) ;  the  cells  are  remarkably  large  and  their  nuclei  are  often  branched; 
the  intima  is  distinctly  striated,  from  the  presence  of  pore-canals.  The 
glands  arise  as  evaginations  of  the  pharynx  (ectodermal)  and  the  chi- 
tinous  intima  of  each  gland  is  cast  at  each  moult,  along  with  the  general 
integument. 


ANATOMY   AND   PHYSIOLOGY 


7.7 


The  silk  glands  of  caddis  worms  (Trichoptera)  are  essentially  like 
those  of  caterpillars  (Lepidoptera)  but  the  glands  of  Neuroptera 
{Chrysopa,  Myrmeleon,  etc.)  Coccinellidae,  Chrysomelidae  and  Syrphidae, 
which  open  into  the  rectum,  are  morphologically  quite  different  frorti 
those  of  Lepidoptera. 

3.  Muscular  System 

The  number  of  muscles  possessed  by  an  insect  is  surprisingly  large. 
A  caterpillar,  for  example,  has  about  two  thousand. 

The  muscles  of  the  trunk  are  segmentally  arranged — most  evidently 


abc 


Fig.  108.  Fig.  109.  Fig.   iio. 

Muscles  of  cockroach;  of  ventral,  dorsal  and  lateral  walls,  respectively,  a,  alary  muscle; 
abc,  abductor  of  coxa;  adc,  adductor  of  coxa;  ef,  extensor  of  femur;  h,  head  muscles;  Is, 
longitudinal  sternal;  It,  longitudinal  tergal;  Ith,  lateral  thoracic;  os,  oblique  sternal;  ot, 
oblique  tergal;  ts,  tergo-stemal;  ts^,  first  tergo-sternal.     After  Miall  and  Denny. 

SO  in  the  body  of  a  larva  or  the  abdomen  of  an  imago,  where  the  muscu- 
lature is  essentially  the  same  in  several  successive  segments.  In  the 
thoracic  segments  of  an  imago,  however,  the  musculature  is,  at  first 
sight,  unlike  that  of  the  abdomen,  and  in  the  head  it  is  decidedly- 
different;  though  future  studies  will  doubtless  show  that  the  thoracit 
and  cephalic  kinds  of  musculature  are  only  modifications  of  the  simplet 
abdominal  type — modifications  brought  about  in  relation  to  the  needs 
of  the  legs,  wings,  mouth  parts,  antennse  and  other  movable  structures. 
The  muscular  system  has  been  generally  neglected  by  students  of 
insect  anatomy;  the  only  comprehensive  studies  upon  the  subject  being 


78 


ENTOMOLOGY 


^ii 


m 


^^ 


Striated    muscle  chitinous  tendons 

fiber  of  an  insect. 

each    of    which    has 


those  of  Straus-Diirckheim  (1828)  on  the  beetle  Melolontha;  Lyonet 
(1762),  Newport  (1834)  and  Lubbock  (1859)  on  caterpillars;  Lubbock 
and  Janet  on  Hymenoptera;  Bauer  (1910)  on  Dytiscus;  and  Berlese 
(1909-13)  on  various  insects. 

The  more  important  muscles  in  the  body  of  a  cockroach 
are  represented  in  Figs.  108-110,  from  Miall  and  Denny. 
The  longitudinal  sternals  with  the  longitudinal  tergals  act 
to  telescope  the  abdominal  segments;  the  oblique  ster- 
nals bend  the  abdomen  laterally;  the  ter go  sternals,  or 
vertical  expiratory  muscles,  draw  the  tergum  and  sternum 
together.  The  muscles  of  the  legs  and  the  wings  have 
already  been  referred  to. 

Structure  of  Muscles. — The  muscles  of  insects  differ 
greatly  in  form  and  are  inserted  frequently  by  means  of 
A  muscle  is  a  bundle  of  long  fibers, 
an  outer  elastic  membrane,  or 
sarcolemma,  within  which  are  several  nuclei;  thus  the  fiber  represents 
several  cells,  which  have  become  confluent.  With  rare  exceptions 
("alary"  muscles  and  possibly  a  few  thoracic  muscles)  the  muscle  fibers 
of  an  insect  present  a  striated  appear- 
ance, owing  to  alternate  light  and  dark 
bands  (Fig.  1 1 1) ,  the  former  being  singly 
refracting,  or  isotropic,  and  the  latter 
doubly  refracting,  or  anisotropic. 

The  minute  structure  of  these  fibers, 
being  extremely  difficult  of  interpreta- 
tion, has  given  rise  to  much  difference  of 
opinion.  The  most  plausible  view  is 
that  of  van  Gehuchten,  Janet  and  others, 
who  hold  that  both  kinds  of  dark  bands 
(Fig.  112)  consist  of  highly  elastic  threads 
of  spongioplasm  (anisotropic)  embedded 
in  a  matrix  of  clear,  semi-fluid,  nutritive 
hyaloplasm  (isotropic).  The  spongio- 
plasmic  threads  of  the  long  bands  extend 

longitudinally  and  those  of  the  short  bands  {"Krause's  membrane'') 
radially,  in  respect  to  the  form  of  the  fiber.  Moreover,  the  attenuated 
extremities  of  the  longitudinal  fibrillae  connect  with  the  radial  fibrill^, 
the  points  of  connection  being  marked  by  sHght  thickenings,  or  nodes, 
which  go  to  make  up  Krause's  membrane. 


Fig.  112. — Minute  structure  of  a 
striated  muscle  fiber.  A ,  longitudinal 
section;  B,  transverse  section  in  the 
region  of  I;  C,  transverse  section  in  the 
region  of  n.  I,  longitudinal  fibrillas; 
n,  Krause's  membrane;  nl,  nucleus; 
r,  radial  fibrillae;  5,  sarcolemma. — After 
Janet. 


ANATOMY   AND    PHYSIOLOGY  79 

Under  nervous  stimulus  a  muscle  shortens  and  thickens  because  its 
component  fibers  do,  and  this  in  turn  is  attributed  to  the  shortening  and 
thickening  of  the  longitudinal  fibrillar.  When  the  stimulus  ceases,  the 
radial  fibrillae,  by  their  elasticity,  possibly  pull  the  longitudinal  ones 
back  into  place.  The  last  word  has  not  been  said,  however,  upon  this 
perplexing  subject. 

Muscular  Power. — The  muscular  exploits  of  insects  appear  to  be 
marvellous  beside  those  of  larger  animals,  though  they  are  often  exag- 
gerated in  popular  writings.  The  weakest  insects,  according  to  Plateau, 
can  pull  five  times  their  own  weight  and  the  average  insect,  over  twenty 
times  its  weight,  while  Donacia  (ChrysomeHdae)  can  pull  42.7  times  its^ 
weight.  As  contrasted  with  these  feats,  a  man  can  pull  in  the  same 
fashion  but  0.86  of  his  weight  and  a  horse  from  0.5  to  0.83.  How  are 
these  differences  explained? 

It  is  incorrect  to  say  that  the  muscles  of  insects  are  stronger  than 
those  of  vertebrates,  for,  as  a  matter  of  fact,  the  contractile  force  of  a 
vertebrate  muscle  is  greater  than  that  of  an  insect  muscle,  other  things 
being  equal.  The  apparently  greater  strength  of  an  insect  in  propor- 
tion to  its  weight  is  accounted  for  in  several  ways.  The  specific  gravity 
of  chitin  is  less  than  that  of  bone,  though  it  varies  greatly  in  both  sub- 
stances. Furthermore,  the  external  skeleton  permits  muscular  attach- 
ments of  the  most  advantageous  kind  as  compared  with  the  internal 
skeleton,  so  that  the  muscles  of  insects  surpass  those  of  vertebrates  as 
regards  leverage.  These  reasons  are  only  of  minor  importance,  how- 
ever. Small  animals  in  general  appear  to  be  stronger  than  larger 
animals  (allowing  for  the  differences  in  weight)  for  the  same  reason  that 
a  smaller  insect  has  more  conspicuous  strength  than  a  larger  one,  when 
the  two  are  similar  in  everything  except  weight.  For  example :  where 
a  bumblebee  can  pull  16.1  times  its  own  weight,  a  honey  bee  can  pull 
20.2;  and  where  the  same  bumblebee  can  carry  while  flying  a  load 
0.63  of  its  own  weight,  the  honey  bee  can  carry  0.78.  Always,  as 
Plateau  has  shown,  the  lighter  of  two  insects  is  the  stronger  in  respect 
to  external  manifestations  of  muscular  force — in  the  ratio  of  this  muscu- 
lar strength  to  its  own  weight. 

To  understand  this,  let  us  assume  that  a  beetle  continues  to  grow  (as 
never  happens,  of  course).  As  its  weight  is  increasing  so  is  its  strength 
— but  not  in  the  same  proportion.  For  while  the  weight — say  that  of  a 
muscle — increases  as  the  cube  of  a  single  dimension,  the  strength  of  the 
muscle  (depending  solely  upon  the  area  of  its  cross-section)  is  increasing 
only  as  the  square  of  one  dimension — its  diameter.     Therefore  the 


8o  ENTOMOLOGY 

increase  in  strength  lags  behind  that  of  weight  more  and  more;  conse- 
quently more  and  more  strength  is  required  simply  to  move  the  insect 
itself,  and  less  and  less  surplus  strength  remains  for  carrying  additional 
weight.  Thus  the  larger  insect  is  apparently  the  weaker,  though 
it  is  actually  the  stronger,  in  that  its  total  muscular  force  is  greater. 

The  writer  uses  this  explanation  to  account  also  for  the  inability  of 
certain  large  beetles  and  other  insects  to  use  their  wings,  though  these 
organs  are  well  developed.  Increasing  weight  (due  to  a  larger  supply 
of  reserve  food  accumulated  by  the  larva)  has  made  such  demands  upon 
the  muscular  power  that  insufhcient  strength  remains  for  the  purpose  of 
flight. 

Statements  such  as  this  are  often  seen — a  flea  can  jump  a  meter,  or 
six  hundred  times  its  own  length.  Almost  needless  to  say,  the  length  of 
the  body  is  no  criterion  of  the  muscular  power  of  an  animal. 

4.  Nervous  System 

The  central  nervous  system  extends  along  the  median  line  of  the  floor 
of  the  body  as  a  series  of  ganglia  connected  by  nerve  cords.  Typically, 
there  is  a  ganglion  (double  in  origin)  for  each  primary  segment,  and  the 
connecting  cords,  or  commissures,  are  paired;  these  conditions  are  most 
nearly  realized  in  embryos  and  in  the  most  generalized  insects  — Thysa- 
nura  (Fig.  113).  In  all  adult  insects,  however,  the  originally  separate 
gangha  consolidate  more  or  less  (Fig.  114)  and  the  commissures  fre- 
quently unite  to  form  single  cords.  Thus  in  Tabanus  (Fig.  1 14,  C)  the 
three  thoracic  gangha  have  united  into  a  single  compound  ganglion 
and  the  abdominal  ganglia  are  concentrated  in  the  anterior  part  of  the 
abdomen;  in  the  grasshopper,  the  nerve  cord,  double  in  the  thorax,  is 
single  in  the  abdomen.  Various  other  modifications  of  the  same  nature 
occur. 

Cephalic  Ganglia. — In  the  head  the  primitive  .ganglia  always  unite 
to  form  two  compound  ganglia,  namely,  the  brain  and  the  sub  (esophageal 
ganglion  (disregarding  a  few  anomalous  cases  in  which  the  latter  is  said 
to  be  absent). 

The  brain,  or  supra  oesophageal  ganglion  (Fig.  115),  is  formed  by  the 
union  of  three  primitive  ganglia,  or  neuromeres  (Fig.  57),  namely,  (i) 
the  protocerebrum,  which  gives  off  the  pair  of  optic  nerves;  (2)  the  deuto- 
cerebrum,  which  innervates  the  antennae;  and  (3)  the  tritocerebrum, 
which  in  Apterygota  bears  a  pair  of  rudimentary  appendages  that  are 
regarded  as  traces  of  a  second  pair  of  antennae. 


ANATOMY   AND   PHYSIOLOGY 


The  suboesophageal  ganglion  (Fig.  115)  is  al- 
ways connected  with  the  brain  by  a  pair  of  nerve 
cords  {cesephageal  commissures)  between  which 
the  oesophagus  passes.  This  ompound  ganglion 
represents  at  most  four  neuromeres:  (i)  mandi- 
bular, innervating  the  mandibles;  (2)  superlin- 
gual,  found  by  the  author  in  Collembola,  but  not 
yet  reported  in  the  less  generahzed  insects;  (3) 
maxillary,  innervating  the  maxilte;  (4)  labial, 
which  sends  a  pair  of  nerves  to  the  labium. 

The  minute  structure  of  the  brain,  thgouh 
highly  complex,  has  received  considerable  study, 
but  will  not  be  described  here  for  the  reason  that 
the  anatomical  facts  are  of  no  general  interest 
so  long  as  their  physiological  interpretation  re- 
mains obscure. 

Sympathetic  System. — ^Lying  along  the 
median  dorsal  line  of  the  oesophagus  is  a  recurrent, 
or  stomato gastric,  nerve  Fig.  116),  which  arises 
anteriorly  in  a  frontal  ganglion  and  terminates 
posteriorly  in  a  stomachic  ganglion  situated  at 
the  anterior  end  of  the  mid  intestine.  Con- 
nected with  the  recurrent  nerve  are  two  pairs  of 
lateral  gangha,  the  anterior  of  which  innervate 
the  dorsal  vessel  and  the  posterior,  the  tracheae 
of  the  head.  The  ventral  nerve  cord  may  include 
also  a  median  nerve  thread  (Fig.  113)  which  gives 
oft"  paired  transverse  nerves  to  the  muscles  of 
the  spiracles. 

Structure  of  Ganglia  and  Nerves. — A  gang- 
lion consists  of  (i)  a  dense  cortex,  composed  of 
ganglion  cells  (Fig.  117),  each  of  which  has  a  large 
rounded  nucleus  and  gives  off  usually  a  single 
nerve  fiber;  and  (2)  a  clear  medullary  portion 
(Punktsubstanz)  derived  from  the  processes  of  the 
cortical  ganglion  cells  and  serving  as  the  place 
of  origin  of  nerve  fibrillas.  There  are,  however, 
ganglion  cells  from  which  processes  may  pass 
directly  into  nerve  fibrillae. 

A  nerve  fiber,  in  an  insect,  consists  of  an  axis- 
cylinder,  composed  of  fibrillae,  and  an  enveloping 
membrane,  or  sheath.  The  axis-cylinder  is  the 
transmitting   portion   and   the  ganglia  are  the 


b-W- 


S"' 


■sy 


III 


Fig.  113. — Central  nerv- 
ous system  of  a  thysanu- 
ran,  Machilis.  The 

thoracic  and  abdominal 
ganglia  are  numbered  in 
succession.  a,  antennal 
nerve;  b,  brain;  e,  com- 
pound eye;  /,  labial  nerve; 
m,  mandibular  nerve;-  mx, 
maxillary  nerve;  o,  ceso- 
phagus;  ol,  optic  lobe;  s, 
suboesophageal  ganglion; 
sy,  sympathetic  nerve. — 
After  GuDEMANS. 


82 


ENTOMOLOGY 


trophic  centers,   i.    e.,   they  regulate  nutrition.     A   nerve   is   always 
either   sensory,   transmitting  impulses  inward  from  a  sense  organ;  or 


Fig.  114. — Successive  stages  in  the  concentration  of  the  central  nervous  system  of  Diptera. 
A,   Chironomus;   B,   Empis;   C,    Tabanus;   D,   Sarcophaga. — After   Brandt. 

else  motor,  conveying  stimuli  from  the  central  nervous  system  outward 
to  muscles,  glands,  or  other  organs. 

Functions." — The  brain  innervates  the  chief  sensory  organs  (eyes  and 
antennae)  and  converts  the  sensory  stimuli  that  it  receives  into  motor 


Pig.  115. — Nervous  system  of  the  head  of  a  cockroach,  a,  antennal  nerve;  ag,  anterior 
lateral  ganglion  of  sympathetic  system;  b,  brain;  d,  salivary  duct;  /,  frontal  ganglion;  h, 
hypopharynx;  I,  labrum;  li,  labium;  m,  mandibular  nerve;  mx,  maxillary  nerve;  nl,  nerve  to 
labrum;  nli,  nerve  to  labium;  o,  optic  nerve;  oc,  oesophageal  commissure;  oe,  oesophagus; 
pg,  posterior  lateral  ganglion  of  sympathetic  system;  r,  recurrent  nerve  of  sympathetic 
system;  s,  suboesophageal  ganglion. — After  Hofer. 

stimuli,  which  effect  co-ordinated  muscular  or  other  movements  in 
response  to  particular  sensations  from  the  environment.  The  brain 
is  the  seat  of  the  will,  using  the  term  "will"  in  a  loose  sense;  it  directs 
locomotor  movements  of  the  legs  and  wings.     An  insect  deprived  of  its 


ANATOMY   AND   PHYSIOLOGY 


83 


brain  cannot  go  to  its  food,  though  it  is  able  to  eat  if  food  be  placed  in 
contact  with  the  end-organs  of  taste,  as  those  ^^       ^ 

of  the  palpi ;  furthermore,  it  walks  or  flies  in  an 
erratic  manner,  indicating  a  lack  of  co-ordina- 
tion of  muscular  action. 

The  suboesophageal  ganglion  controls  the 
mouth  parts,  co-ordinating  their  movements  as 
well  as  some  of  the  bodily  movements. 

The  thoracic  ganglia  govern  the  appendages 
of  their  respective  segments.  These  ganglia 
and  those  of  the  abdomen  are  to  a  great  extent 
independent  of  brain  control,  each  of  these 
ganglia  being  an  individual  motor  center  for 
its  particular  segment.  Thus  decapitated  in- 
sects are  still  able  to  breathe,  walk  or  fly,  and 
often  retain  for  several  days  some  power  of 
movement. 

In  regard  to  the  sympathetic  system,  it 
has  been  shown  experimentally  that  the  fron- 
tal ganglion  controls  the  swallowing  movements 
and  exerts  through  the  stomatogastric  nerve 
a  regulative  action  upon  digestion.  The  dor- 
sal sympathetic  system  controls  the  dorsal 
vessel  and  the  salivary  glands,  while  the 
ventral  sympathetic  system  is  concerned  with 
the  spiracular  muscles. 

5.  Sense  Organs 
For   the  reception  of  sensory  impressions 
from  the  external  world,  the  armor-Hke  integu- 
ment of  insects  is  modified  in  a  great  variety  of  ways.     Though  sense 


Fig.  116.— Sympathetic  nerv- 
ous system  of  an  insect, 
diagrammatically  represented. 
a,  antennal  nerve;  b,  brain;  /,■ 
frontal  ganglion;  I,  I,  paired 
lateral  ganglia;  m,  nerves  to 
upper  mouth  parts;  o,  op- 
tic nerve;  r,  recurrent 
nerve;  5,  nerve  to  saUvary 
glands;  st,  stomachic  ganglion. 
— After  KoLBE. 


Fig.  117.— Transverse  section  of  an  abdominal  gangUon  of  a  caterpillar.     /,  nerve  fibers;  g, 
gangUon  cells;  w,  nerve  sheath;  p,  Punktsubstanz. 


84  ENTOMOLOGY 

organs  of  one  kind  or  another  may  occur  on  almost  any  part  of  an 
insect,  they  are  most  numerous  and  varied  upon  the  head  and  its  appen- 
dages, particularly  the  antennae. 

Anteimal  Sensilla. — Some  idea  of  the  diversity  of  form  in  antennal 
sense  organs  may  be  obtained  from  Figs.  1 18-127,  taken  from  a  paper 
by  Schenk,  whose  useful  classification  of  antennal  sensilla,  or  sense 
organs,  is  here  outlined: 

1.  Sensillum  cceloconicum — a  conical  or  peg-like  projection  immersed 
in  a  pit  (Figs.  118,  119).     In  all  probability  olfactory. 

2.  S.  hasiconicum — a  cone  projecting  above  the  general  surface  (Fig. 
120).     Probably  olfactory. 

3.  S.  styloconicum — a  terminal  tooth  or  peg  seated  upon  a  more  or 
less  conical  base  (Fig.  121).     Olfactory. 

4.  S.  chaticum — a  bristle-like  sense  organ  (Fig.  122).     Tactile. 

5.  S.  trichodeum — a  hair-hke  sense  organ  (Figs.  123,  124).     Tactile. 

6.  S.  placodeum —  a  membranous  plate,  its  outer  surface  continuous 
with  the  general  integument  (Fig.  125).  Function  doubtful;  not  audi- 
tory and  probably  not  olfactory,  though  the  function  is  doubtless  a 
mechanical  one;  Schenk  suggests  that  this  organ  is  affected  by  air 
pressure,  as  when  a  bee  or  wasp  is  moving  about  in  a  confined  space. 

7.  S.  ampullaceum — a  more  or  less  flask-shaped  cavity  with  an 
axial  rod  (Figs.  126,  127).     Probably  auditory. 

These  types  of  sensilla  will  be  referred  to  in  physiological  order. 

Touch.^The  tactile  sense  is  highly  developed  in  insects,  and  end- 
organs  of  touch,  unlike  those  of  other  senses,  are  commonly  distributed 
over  the  entire  integument,  though  the  antennae,  palpi  and  cerci  are 
especially  sensitive  to  tactile  impressions. 

The  end-organs  of  touch  are  bristles  (sensilla  chastica)  or  hairs 
(sensilla  trichodea),  each  arising  from  a  special  hypodermis  ceU  and 
having  connection  with  a  nerve.  SensiUa  chsetica  doubtless  receive 
impressions  from  foreign  bodies,  while  sensilla  trichodea,  being  best 
developed  in  the  swiftest  flying  insects  and  least  so  in  the  sedentary 
forms,  may  be  affected  by  the  resistance  of  the  air,  when  the  insect  or 
the  air  itself  is  in  motion. 

Not  all  the  hairs  of  an  insect  are  sensory,  however,  for  many  of  them 
have  no  nerve  connections. 

In  blind  cave  insects  the  antennae  are  very  long  and  are  exquisitely 
sensitive  to  tactile  impressions. 

Taste. — The  gustatory  sense  is  unquestionably  present  in  insects,  as 
is  shown  both,  by  common  observation  and  by  precise  experimentation. 


ANATOMY   AND   PHYSIOLOGY 


85 


Will  fed  wasps  with  sugar  and  then  replaced  it  with  powdered  alum, 
which  the  wasps  unsuspectingly  tried  but  soon  rejected,  cleaning  the 
tongue  with  the  fore  feet  in  a  comical  manner  and  manifesting  other 


Figs,  i  18-12  7. — Types  of  antennal  sensilla,  in  longitudinal  section  (excepting  Figs.  121 
and  122).  Fig.  118,  sensillum  coeloconicum ;  119,  coeloconiciim;  120,  basiconicum;  121, 
styloconicum;  122,  chaeticum;  123,  trichodeum;  124,  trichodeum;  125,  placodeum;  126, 
ampuUaceum;  127,  ampullaceum;  c,  cuticula;  h,  hypodermis;  n,  nerve;  5.  sensory  cell. 
Figs.  118,  120,  123,  125,  126,  honey  bee,  Apis  mellifera;  119,  121,  124,  Fidonia  piniaria; 
122,  moth,  Ino  pruni;  127  wasp,  Vespa  crabro. — After  Schenk. 

signs  of  what  we  may  call  disgust.  Forel  offered  ants  honey  mixed  with 
morphine  or  strychnine;  the  ants  began  to  feed  but  at  once  rejected  the 
mixture.  In  its  range,  however,  the  gustatory  sense  of  insects  differs 
often  from  that  of  man.     Thus  Will  found  that  Hymenoptera  refused 


86  ENTOMOLOGY 

honey  with  which  a  very  httle  glycerine  had  been  mixed  (though  Musci- 
dse  did  not  object  to  the  glycerine)  and  Forel  found  that  ants  ate  un- 
suspectingly a  mixture  of  honey  and  phosphorus  until  some  of  them 
were  killed  by  it.  Under  the  same  circumstances,  man  would  be  able 
to  detect  the  phosphorus  but  not  the  glycerine. 

Location  of  Gustatory  Organs. — As  would  be  expected,  the  end- 
organs  of  taste  are  situated  near  the  mouth,  commonly  on  the  hypo- 
pharynx  (Fig.  128),  epipharynx  and  maxillary  palpi.  On  the  tongue  of 
the  honey  bee  the  taste  organs  appear  externally  as  short  setae  (Fig.  129) 
and  on  the  maxillae  of  a  wasp  as  pits,  each  with  a  cone,  or  peg,  project- 
ing from  its  base  (Figs.  130,  131).     Similar  taste  pits  and  pegs  were 


Pig.   128. — -Section  through  tongue  of  wasp,  Vespa  vul-  Fig.  129. — Tongue  of  honey 

garis.     c,  cuticula;  g,  gland  cell;  h,  hypodermis;  «,  nerve;  hee,  Apis  mellifera.    /»,  protect- 

ob,  gustatory  bristle;  ph,  protecting  hair;  sc,  sensory  cell;  ing  bristles;  s,  terminal  spoon; 

tb,  tactile  bristle. — After  Will.  /,  taste  setae. — After  "Will. 

found  by  Packard  on  the  epipharynx  in  most  of  the  mandibulate  orders 
of  insects. 

Histology. — The  end-organs  of  taste  arise  from  special  hypodermis 
cells,  as  minute  setae  or,  more  commonly,  pegs,  each  seated  in  a  pit,  or 
cup,  and  connected  with  a  nerve  fiber  (Figs.  131,  132).  In  some  cases, 
however,  it  is  difficult  to  decide  whether  a  given  organ  is  gustatory  or 
olfactory,  owing  to  the  similarity  between  these  two  kinds  of  structures. 
In  aquatic  insects,  indeed,  the  senses  of  taste  and  smell  are  not  differen- 
tiated, these  forms  having  with  other  of  the  lower  animals  simply  a 
"chemical"  sense. 

Smell. — In  most  insects  the  sense  of  smell  is  highly  efficient  and  in 
many  species  it  is  inconceivably  acute.  Hosts  of  insects  depend  chiefly 
on  their  olfactory  powers  to  find  food,  for  example  many  beetles,  the 
flesh  flies  and  the  flower-visiting  moths;  or  else  to  discover  the  opposite 


ANATOMY   AND   PHYSIOLOGY 


87 


sex,  as  is  notably  the  case  in  saturniid  moths.     In  dragon  flies,  however, 
this  sense  is  reHed  upon  far  less  than  that  of  sight. 

Organs  of  Smell.^By  means  of  simple  but  conclusive  experiments, 
Hauser  and  others  have  shown  that  the  antennae  are  frequently  olfactory 
— though  not  to  the  exclusion  of  tactile  or  auditory  functions,  of  course. 
Hauser  found  that  ants,  wasps,  various  flies,  moths,  beetles  and  larvae, 
which  react  violently  toward  the  vapor  of  turpfentine,  acetic  acid  and 
other  pungent  fluids,  no  longer  respond  to  the  same  stimuli  after  their 
antennae  have  been  amputated  or  else  covered  with  paraffine  to  exclude 

the  air.  His  experiments  were  con- 
ducted under  conditions  such  that  the 
results  could  not  be  ascribed  to  the  shock 
of  the  operation  or  to  effects  upon  the 
gustatory  or  respiratory  systems;  except 
for  having  lost  the  sense  of  smell,  the 
insects  experimented  upon  behaved  in 
, _  __  a  normal  manner.     It  should  be  said, 


Fig.  130. — Under  side  of  left  maxilla 
of  wasp,  Vespa  vulgaris,  p,  palpus; 
pr,  protecting  hairs;  tc,  taste  cup;  th, 
tactile  hair. — After  Will. 


Fig.  131. — Longitudinal  section  of  gustatory 
end-organ  (tc,  of  Pig.  130).  c,  cuticula;  k,  hypo- 
dermis;  sc,  sensory  cell;  tc,  taste  cup. — After 
Will. 


however,  that  Carabus,  Melolontha  and  Silpha  still  reacted  to  some 
extent  toward  strong  vapors  even  after  the  extirpation  of  the  antennae; 
while  in  Hemiptera  the  loss  of  the  antennae  did  not  lessen  the  response 
to  the  odors  used.  These  facts  indicate  that  the  sense  of  smell  is  not 
always  confined  to  the  antennae;  indeed  the  maxillary  palpi  are  frequently 
olfactory,  as  in  Silpha  and  Hydaticus;  also  the  cerci,  as  in  the  cock- 
roach and  other  Orthoptera.  Experiments  indicate  that  an  insect  per- 
ceives some  odors  by  means  of  the  antennae  and  others  by  the  palpi 
or  other  organs.  Hauser  found  that  the  flies  Sarcophaga  and  Calli- 
phora,  after  the  amputation  of  their  antennae,  became  quite  indifferent 
toward  decayed  meat,  to  which  they  had  previously  swarmed  with 


88  ENTOMOLOGY 

great  persistence,  though  their  actions  in  all  other  respects  remained 
normal.  Males  of  many  moths  and  a  few  beetles  are  unable  to  find 
the  females  (see  beyond)  when  the  former  are  deprived  of  the  use  of 
their  antennae. 


Fig.  132. — Taste  cup  from  maxilla  of 
Bombus.  sc,  sensory  cell;  n,  nerve. — After 
Will. 


Fig.  133. — Section  of  antennal  olfactory 
organ  of  grasshopper,  Caloptenus.  c,  cutic- 
ula;  m,  membrane;  n,  nucleus  of  sensory 
cell;  nv,  nerve;  p,  pit  with  olfactory  peg, 
pg,  pigment. — After  Hauser. 


End-Organs. — Structures  which  are .  regarded  as  olfactory  end- 
organs  occur  commonly  on  the  antennae,  often  on  the  maxillary  and 
labial  palpi  and  sometimes  on  the  cerci.  These  end-organs  are  hypo- 
dermal  in  origin  and  consist,  generally  speaking,  of  a  multinucleate 
cell  (Fig.  133)  penetrated  by  a  nerve  and  prolonged  into  a  chitinous 
bristle  or  peg,  which  is  more  or  less  enclosed  in  a  pit,  as  in  Tahanus 
(Fig.  134).  In  many  instances,  however,  the  end-organs  take  the 
form  of  teeth  or  cones  projecting  from  the  general  surface  of  the  antenna, 
as  in  Vespa  (Fig.  135).  These  cones  are  usually  less  numerous  than 
the  pits;  in  Vespa  crahro,  for  example,  the  teeth  number  700  and  the 
pits  from  13,000  to  14,000  on  each  antenna.  The  pits  are  even  more 
numerous  in  some  other  insects;  thus  there  are  as  many  as  17,000  on 
each  antenna  of  a  blow  fly  (Hicks).  The  male  of  Melolontha  vulgaris, 
which  seeks  out  the  female  by  the  sense  of  smell,  has  according  to 
Hauser  39,000  pits  on  each  antenna,  and  the  female  only  35,000.  Pits 
presumably  olfactory  in  function  have  been  found  by  Packard  on  the 
maxillary  and  labial  palpi  of  Perla  and  on  the  cerci  of  the  cockroach, 
Periplaneta  atnericana.     Vom  Rath  has  described  four  kinds  of  sense 


ANATOMY    AND    PHYSIOLOGY 


89 


hairs  from  the  two  larger  of  the  four  caudal  appendages  of  a  cricket, 
Gryllus;  some  of  these  (Fig.  136)  may  be  olfactory,  though  possibly 
tactile.  The  same  author  found  on  the  terminal  palpal  segment  in 
various  Lepidoptera  a  large  flask-shaped  invagination  (Fig.  137)  into 
which  project  numerous  chitinous  rods,  each  a  process  of  a  sensory 
cell,  which  is  supplied  by  a  branch  of  the  principal  palpal  nerve;  these 
peculiar  organs  are  inferred  to  be  olfactory. 

The  chief  reason  for  regarding  these  various  end-organs  as  olfactory 
is  that  they  appear  from  their  structure  to  be  better  adapted  to  receive 
that  kind  of  an  impression  than  any 
other,  so  far  as  we  can  judge  from  our 
own  experience.  Though  it  is  easy  to 
demonstrate  that  the  antennae,  for  ex- 
ample, are  olfactory,  it  frequently  hap- 


FiG.  134. — Section  through  antennal  olfactory 
pit  of  fly,  Tabanus.  c,  cuticula;  p,  pit  with  peg; 
pb,  protecting  bristles;  s,  sensory  cell. — After 
Hauser. 


Fig.  135. — Longitudinal  section  of 
antennal  olfactory  organ  of  wasp, 
Vespa.  c,  olfactory  cell;  en,  olfactory 
cone;  ct,  cuticula;  h,  hypodermis  cells; 
n,  nerve;  r,  rod. — After  Hauser. 


pens  that  the  antennae  bear  several  distinct  forms  of  sensory  end-organs,  so 
minute  and  intermingled  that  their  physiological  differences  can  scarcely 
be  ascertained  by  experiment  but  must  be  inferred  from  their  peculiarities 
of  structure.  Schenk,  however,  has  arrived  at  precise  results  by  compar- 
ing the  an.tennal  sensilla  in  the  two  sexes,  selecting  species  in  which  the 
antennae  exhibit  a  pronounced  sexual  dimorphism,  in  correlation  with  sex- 
ual differences  of  behavior.  Taking  Notolophus  aniiqua,  in  which  the 
male  seeks  out  the  female  by  means  of  antennal  organs  of  smell,  he 
finds  that  the  male  has  on  each  antenna  about  600  sensilla  cceloconica 
and  the  female  only  75;  similarly  in  the  geometrid  Fidonia,  in  which 
the  ratio  is  350  to  100.  The  sensilla  styloconica  also,  of  these  two 
genera,  are  regarded  as  olfactory  organs.     These  two  kinds  of   end- 


90 


ENTOMOLOGY 


organs  are  not  only  structurally  adapted  for  the  reception  of  olfactory 
stimuli,  but  their  numerical  differences  accord  with  the  observed  differ- 
ences in  the  olfactory  powers  of  the  two  sexes,  there  being  no  other 
antennal  end-organs  to  enter  into  the  consideration. 

Dr.  N.  E.  Mclndoo  has  denied  that  the  antennae  are  olfactory 
organs.  He  finds,  in  all  the  large  orders  of  insects,  and  on  almost  all 
parts  of  the  body  and  legs,  on  the  bases  of  the  wings,  and  in  other  situa- 
tions, the  structures  that  he  terms  olfactory  pores,  to  which  he  has 
devoted  an  immense  amount  of  study. 

Assembling. — It  is  a  fact,  well  known  to  entomologists,  that  the 
females  of  many  moths  and  some  beetles  are  able  by  emitting  an  odor  to 


Fig.  136. — Longitudinal  section  of  a  por- 
tion of  a  caudal  appendage  of  a  cricket, 
Gryllus  domeslicus.  b,  bladderlike  hair;  c, 
cuticula;  h,  hypodermis;  n,  nerve;  ns,  non- 
sensory  setae;  sc,  sense  cell;  sh,  sensory  hair. 
— After  VOM  Rath. 


Fig.  137. — Longitudinal  section  of  apex 
of  palpus  of  Pier  is.  c,  cuticula;  h,  hypo- 
dermis; «,  nerve;  s,  scales;  5C,  sense  cells. — 
After  VOM  Rath. 


attract  the  opposite  sex,  often  in  considerable  numbers.  Under  favor- 
able conditions,  a  freshly  emerged  female  of  the  promethea  moth,  exposed 
out  of  doors  in  the  latter  part  of  the  afternoon,  will  attract  scores  of  the 
males.  A  breeze  is  essential  and  the  males  come  up  against  the  wind; 
if  they  pass  the  female,  they  turn  back  and  try  again  until  she  is  located, 
vibrating  the  antennas  rapidly  as  they  near  her.  The  female,  mean- 
while, exhales  an  appreciable  odor,  chiefly  from  the  region  of  the  ovi- 
positor, and  males  will  congregate  on  the  ground  at  a  spot  where  a 
female  has  been.  If  one  of  these  males  is  deprived  of  the  use  of  his 
antennae,  however,  he  flutters  about  in  an  aimless  way  and  is  no  longer 
able  to  find  the  female. 

Among  beetles,  males  of  Polyphylla  gather  and  scratch  at  places 


ANATOMY   AND   PHYSIOLOGY  9 1 

where  females  are  about  to  emerge  from  the  ground.  Prionus  also 
assembles,  as  Mrs.  Dimmock  observed  in  Massachusetts.  In  this 
instance  many  males,  with  palpitating  antennae,  ran  and  flew  to  the 
female;  moreover,  a  number  oi  females  were  attracted  to  the  scene. 

Sounds  of  Insects. — Before  considering  the  sense  of  hearing,  some 
account  of  the  sounds  of  insects  is  desirable.  Most  of  these  are  made  by 
the  vibrations  of  a  membrane  or  by  the  friction  of  one  part  against 
another. 

The  wings  of  many  Diptera  and  Hymenoptera  vibrate  with  sufficient 
speed  and  regularity  to  give  a  definite  note.  The  wing  tone  of  a  honey 
bee  is  A'  and  that  of  a  common  house  fly  is  F'.  From  the  pitch  the 
number  of  vibrations  may  be  determined;  thus  ^'  means  440^  vibrations 
per  second  and  F',  352.  The  numbers  thus  ascertained  may  be  verified 
by  Marey's  graphic  method  (Fig.  76) ;  he  found  that  the  fly  referred  to 
actually  made  330  strokes  per  second  against  the  smoked  surface  of  a 
revolving  cylinder. 

Flies,  bees,  dragon  flies  and  some  beetles  make  buzzing  or  humming 
sounds  by  means  of  the  spiracles,  there  being  behind  each  spiracle  a 
membrane  or  chitinous  projection  which  vibrates  during  respiration. 
This  "voice"  should  be  distinguished  from  the  wing  tone  when  both 
are  present,  as  in  bees  and  flies.  A  fly  will  buzz  when  held  by  the 
wings,  and  some  gnats  continue  to  buzz  after  losing  wings,  legs  and 
head.  The  wing  tone  is  the  more  constant  of  the  two;  in  the  honey  bee 
it  is  ^',  falling  to  E'  if  the  insect  is  tired,  while  the  spiracular  tone  of  the 
same  insect  is  at  least  an  octave  higher  {A")  and  often  rises  to  B"  or 
C",  according  to  the  state  of  the  nervous  system;  in  fact,  it  is  possible 
and  even  probable  that  various  spiracular  tones  express  different 
emotions,  as  is  indicated  by  the  effects  produced  by  the  voice  of  the  old 
queen  bee  upon  the  young  queens  and  the  males. 

The  well-known  ''shrilling"  of  the  male  cicada  is  produced  by  the 
rapid  vibration  of  a  pair  of  membranes,  or  drums,  situated  on  the  basal 
abdominal  segment,  and  vibrated  each  by  means  of  a  special  muscle. 

Frictional  sounds  are  made  by  beetles  in  a  great  variety  of  ways :  by 
the  rubbing  of  the  pronotum  against  the  mesonotum  (many  Cerambyci- 
dae) ;  or  of  abdominal  ridges  against  elytral  rasps  {Elaphrus,  Cychrus) ; 
or  two  dorsal  abdominal  rasps  against  specialized  portions  of  the  wing 
folds  (Passalus  cornutus),  not  to  mention  other  methods.  In  most  cases 
one  part  forms  a  rasp  and  the  other  a  scraper,  for  the  production  of 
sound. 

^  Upon  the  basis  of  C  as  264  vibrations  per  second.  The  C  of  the  physicist  has  256  as 
its  frequency  of  vibration. 


92  ENTOMOLOGY 

In  many  of  these  instances  the  sound  serves  to  bring  the  two  sexes 
together  and  is  not  necessarily  confined  to  one  sex;  thus  in  Passalus  cor- 
nutus  both  sexes  stridulate,  and  the  larva  as  well. 

A  few  moths  (Sphingidae)  and  a  few  butterflies  make  sounds;  the 
South  American  butterfly  Ageronia  feronia  emits  a  sharp  crackling 
noise  as  it  flies.  A  rasp  and  a  scraper  have  been  found  in  several  ants, 
though  ants  very  seldom  make  any  sounds  that  can  be  distinguished 
by  the  human  ear;  Mutilla,  however,  makes  a  distinct  squeaking  sound 
by  means  of  a  stridulating  organ  similar  to  those  of  ants. 

Stridulating  organs  attain  their  best  development  in  Orthoptera,  in 
which  group  the  abihty  to  stridulate  is  often  restricted  to  the  male, 
though  not  so  often  as  is  commonly  supposed.  Among  Locustidae, 
Stenohothrus  rubs  the  hind  femora  against  the  tegmina  to  make  a 
sound,  the  femur  bearing  a  series  of  teeth,  which  scrape  across  the 
elevated  veins  of  the  wing-cover;  while  the  male  of  Dissosteira  makes  a 
crackling  sound  during  flight  or  while  poising,  by  means  of  friction 
between  the  front  and  hind  wings,  where  the  two  overlap. 

Tettigoniidae  and  Gryllidae  stridulate  by  rubbing  the  bases  of  the  teg- 
mina against  each  other.  Thus  in  the  male  Microcentrum  laurifolium 
the  left  tegmen,  which  overlaps  the  right,  bears  a  file-like  organ  of  about 
fifty-five  teeth  (Fig.  138),  while  the  opposite  tegmen  bears  a  scraper,  at 
right  angles  to  the  file.  The  tegmina  are  first  spread  a  little;  then,  as 
they  close  gradually,  the  scraper  clicks  across  the  teeth,  making  from 
twenty  to  thirty  sharp  "tic"-  like  sounds  in  rapid  succession.  This 
call  guides  the  female  to  the  male  and  when  they  are  a  few  inches  apart 
she  makes  now  and  then  a  short,  soft  chirp,  to  which  he  responds  with  a 
similar  chirp,  which  is  quite  unlike  the  first  call  and,  moreover,  is 
made  by  the  opening  of  the  tegmina.  These  and  other  details  of  the 
courtship  may  readily  be  observed  in  twilight  and  even  under  artificial 
light,  as  the  latter,  if  not  too  strong,  does  not  disturb  the  pair.  Some- 
thing similar  may  be  observed  in  the  daytime  in  Orchelimum,  Xiphidium 
and  the  tree  crickets,  (Ecanthus.  The  stridulating  areas  are  usually 
membranous  and. the  rasping  organs  are  modified  veins.  Frequently 
the  wing-covers  bulge  out  to  form  a  resonant  chamber  that  reinforces 
the  sound,  as  in  the  katydid. 

The  naturalist  can  recognize  many  a  species  of  grasshopper  by  its 
song;  Scudder  has  expressed  some  of  these  songs  in  musical  notation. 
The  usual  song  of  the  common  meadow-grasshopper,  Orchelimum  vul- 
gare,  may  be  represented  by  a  prolonged  zr  .  .  .  sound,  followed  by 
a  staccato  jip-jip-jip-jip.    .    .    . 


ANATOMY  AND   PHYSIOLOGY 


93 


In  Orthoptera,  the  frequency  of  stridulation  increases  with  the  tem- 
perature; and  the  correlation  between  the  two  is  so  close  that  it  is  easy 


Fig.  138. — Stridulating  organs  of  Microcentrum  laurifolium.  A,  dorsal  aspect  of 
file  (st)  when  the  tegmina  are  closed;  B,  ventral  aspect  of  left  tegmen  to  show  file;  C,  dorsal 
aspect  of  right  tegmen  to  show  scraper  (s). 


to  compute  the  temperature  from  the  number  of  calls  per  minute,  by 
means  of  formulae.  The  formula  for  a  common  cricket  [probably  a 
tree-cricket,  CEcanthus  niveus],  as  given  by  Professor  Dolbear,  is 

r  =  50  H ,  which  simplified  is  T  =  40  H 

4  4 

Here  T  stands  for  temperature  and  N,  the  rate  per  minute. 

A  similar  formula  for  the  katydid   {Cyrtophyllus  perspicillatus) , 
based  upon  observations  made  by  R.  Hayward,  would  be 


r  =  60  + 


N-  ig 


Here,  in  computing  N,  either  the  "katy-did"  or  the  "she-did"  is  taken 
as  a  single  call. 


94  ENTOMOLOGY 

Professor  A.  F.  Shull,  who  has  made  precise  observations  on  the 
stridulation  of  (Ecanthus,  finds  that  there  are  numerous  variations  of. 
rate  that  cannot  be  accounted  for  by  differences  of  temperature;  that 
Dolbear's  formula  cannot  be  appHed  without  a  possible  error  of  6.65° 
F.;  that  humidity  seems  to  affect  the  rate  of  chirping  and  that  crickets 
show  a  certain  individuality  in  their  manner  of  chirping  under  the  same 
external  conditions. 

Hearing. — There  is  no  doubt  that  insects  can  hear.  The  presence 
of  sound-making  organs  is  strong  presumptive  evidence  that  the  sense  of 
hearing  is  present.  Female  grasshoppers  and  beetles  make  locomotor 
and  other  responses  to  the  sounds  of  the  males,  and  male  grasshoppers 
will  answer  the  counterfeit  chirping  made  with  a  quill  and  a  file. 

Auditory  organs  are  not  restricted  to  any  one  region  of  an  insect,  but 
occur,. according  to  the  species,  on  antennae,  abdomen,  legs,  or  elsewhere. 

The  antennae  of  some  insects  are  evidently  stimulated  by  certain 
notes,  particularly  those  made  by  their  own  kind.  Thus  the  antennae 
of  the  male  mosquito  are  auditory,  as  proved  by  the  well-known  experi- 
ments of  Mayer.  He  fastened  a  male  Culex  to  a  microscope  slide  and 
sounded  various  tuning  forks.  Certain  tones  caused  certain  of  the 
antennal  hairs  to  vibrate  sympathetically,  and  the  greatest  amount  of 
vibration  occurred  in  response  to  512  vibrations  per  second,  or  the  note 
C",  which  is  approximately  the  note  upon  which  the  female  hums. 
The  male  probably  turns  his  head  until  the  two  antennae  are  equally 
affected  by  the  note  of  the  female,  when,  by  going  straight  ahead,  he  is 
able  to  locate  her  with  great  precision. 

In  the  lack  of  experimental  evidence,  other  organs  are  inferred  to  be 
auditory  on  account  of  their  structure.  Locustidae  bear  on  each  side  of 
the  first  abdominal  segment  a  tympanal  sense  organ — the  subject  of 
Graber's  well-known  figure  (Fig.  139) .  This  organ  is  admirably  adapted 
to  receive  and  transmit  sound-waves.  The  tympanum,  or  membrane, 
is  tense,  and  can  vibrate  freely,  as  the  air  pressure  against  the  two  sur- 
faces of  the  membrane  is  equalized  by  means  of  an  adjacent  spiracle, 
which  admits  air  to  the  inner  surface.  Resting  against  the  inner  face 
of  the  tympanum  are  two  processes  (Fig.  139,  p,  p),  which  serve  proba- 
bly to  transfer  the  vibrations,  and  there  is  also  a  delicate  vesicle  con- 
nected by  means  of  an  intervening  ganglion  with  the  auditory  nerve, 
which  in  this  case  comes  from  the  metathoracic  ganghon.  The  nerve 
terminations  consist  of  delicate  bristle-like  processes  which  are  probably 
affected  by  the  oscillations  of  the  fluid  contained  in  the  vesicle  just 
referred  to. 


ANATOMY   AND   PHYSIOLOGY 


95 


Other  tympanal  organs,  doubtless  auditory,  are  found  on  the  fore 
tibiae  of  Tettigoniidas,  ants,  termites  and  PerHda),  on  the  femora  of  Pedicu- 
hdae  and  the  tarsi  of  some  Coleoptera. 

Several  types  of  diordotonal  organs  have  been  described,  of  which 
those  of  the  transparent  Core/Ara  larva  may  serve  as  an  example.  These 
organs,  situated  on  each  side  of  abdominal  segments  4-10,  inclusive, 
consist  each  (Fig.  140)  of  a  tense  cord,  probably  capable  of  vibration, 
which  is  attached  at  its  posterior  end  to  the  integument  and  at  its 


-i^ 


Fig.  139. — Inner  aspect  of  right  tympanal  sense 
organ  of  a  grasshopper,  Caloplenus  italicus.  b.  chitin- 
ous  border;  c,  closing  muscle  of  spiracle;  gn,  gan- 
glion; m,  tympanum;  n,  nerve;  o,  opening  muscle 
of  spiracle;  p,  p,  processes  resting  against  tympan- 
um; s,  spiracle;  tm,  tensor  muscle  of  tympanum;  v, 
vesicle.     After  Graber. 


Fig.  140. — Chordotonal  sense 
organ  of  aquatic  dipterous  larva, 
Corethra  plumicornis.  cd,  cord;  eg, 
chordotonal  ganglion;  /,  fibers  of  an 
,  integumental  nerve;  g,  ganglion  of 
ventral  chain;  I,  ligament;  m,  lon- 
gitudinal mujcles;  n,  chordotonal 
nerve;  r,  rods  (nerve  terminations); 
t,  tactile  setae. — After  Graber. 

anterior  end  to  a  ligament.  Between  the  cord  and  the  supporting 
ligament  is  a  small  ganglion,  which  receives  a  nerve  from  the  principal 
ganglion  of  the  segment. 

Vision. — The  external  characters  of  the  two  kinds  of  eyes — ocelli  and 
compound  eyes — have  already  been  described.  While  the  lateral  ocelli 
are  comparatively  simple  in  structure,  consisting  of  a  small  number  of 
cells,  the  dorsal  ocelli  almost  rival  the  compound  eyes  in  complexity. 

Dorsal  Ocelli. — These  consist  (Fig.  141)  of  (i)  lens,  (2)  vitreous 
body,  (3)  retina,  (4)  nerve  fibers,  (5)  pigmented  hypodermis  cells,  and  (6) 


96 


ENTOMOLOGY 


accessory  cells,  between  the  retinal  cells  and  the  nerve  fibers.  The  lens, 
usually  biconvex  in  form,  is  a  local  thickening  of  the  general  cuticula; 
it  is  supplemented  in  its  function  by  the  vitreous  body,  consisting  of  a 
layer  of  transparent  hypodermis  cells;  these  in  many  insects  are  elon- 
gate, constituting  a  vitreous  layer  of  rather  more  importance  than  the 
one  represented  in  Fig.  141.  The  retina  consists 
of  cells  more  or  less  spindle-shaped  and  associated 
in  pairs  or  in  groups  of  two  or  three,  each  group 
being  termed  a  retinula.  The  basal  end  of  each 
retinal  cell  is  continuous  with  a  nerve  fiber  (Fig. 
142),  according  to  Redikorzew  and  others,  and  in 


Fig.  141. — Median  ocellus  of  honey  bee,  Apis  mellifera,  in 
sagittal  section,  h,  hypodermis;  /,  lens;  n,  nerve;  p,  iris  pigment; 
r,  retinal  cells;  v,  vitreous  body. — After  Redikorzew. 


— n 


Fig.  142. — An  ocel- 
lar  retinula  of  the  honey 
bee,  composed  of  two 
retinal  cells.  A,  longi- 
tudinal section;  B, 
transverse  section;  n, 
n,  nerves;  p,  pigment; 
r,  rhabdom.- After  Red- 
ikorzew. 


some  instances  (Calopteryx)   a  nerve  fiber  enters 
the  cell.     Each  retinula  contains  a  longitudinal 
rod,  or  rhabdom,  in  the  secretion  of  which  all  the 
cells  of  the  retinula  are  concerned.     Between  the 
retinal  cells  and  nerve  fibers  are  indifferent,  or  accessory  cells.  Pig- 
ment granules,  usually  black,  are  contained  in  these  cells,  also  in 
the  retinal  cells  and  around  the  lens,  in  the  last  instance  forming  the 
iris. 

Vision  by  Ocelli.— Though  the  ocellus  is  constructed  on  somewhat 
the  same  plan  as  the  human  eye,  its  capacity  for  forming  images  must 


ANATOMY    AND    PHYSIOLOGY 


97 


be  extremely  limited;  for  since  the  form  of  the  lens  is  fixed  and  also  the 
distance  between  the  lens  and  the  retina,  there  is  no  power  of  accom- 
modation, and  most  external  objects  are  out  of  focus;  to  make  an 
image,  then,  the  object  must  be  at  one  definite  distance  from  the  lens, 
and  as  the  lens  is  usually  strongly  convex,  this  distance  must  be  small; 
in  other  words,  insects,  like  spiders,  are  very  near-sighted,  so  far  as  the 
oceUi  are  concerned;  furthermore,  the  small  number  of  retinal  rods 
implies  an  image  of  only  the  coarsest  kind. 

If  the  compound  eyes  of  a  grasshopper  are  covered  with  an  opaque 
varnish  and  the  insect  is  placed  in  a  box  with  only  a  single  opening,  it 
readily  finds  its  way  out  by  means  of  its  ocelli;  if  the  three  ocelli  also 
are  covered,  however,  it  no  longer  does  so, 
except  by  accident,  though  it  can  make  its 
escape  when  only  one  of  the  ocelli  is  left 
uncovered.  The  ocelli,  then,  can  distinguish 
light  from  darkness — and  they  are  probably 
more  serviceable  to  the  insect  in  this  way 
than  in  forming  images. 

Compound  Eyes. — As  regards  delicacy  and 
intricacy  of  structure,  the  compound  eye  of 
an  insect  is  scarcely  if  at  all  inferior  to  the  eye 
of  a  vertebrate.  In  radial  section  (Fig.  143), 
a  compound  eye  appears  as  an  aggregation 
of]  similar  elongate  elements,  or  ommaiidia, 
each  of  which  ends  externally  in  a  facet.     The      ^'"y  ^43.-Portion  of  com- 

•'  pound    eye    of    fly,     Calltphora 

following  structures  compose,  or  are  concerned  vomitoria,  radial  section,     c,  cor- 

.,1  1  ,.j.  /    \  /   \  nea;    i,   iris   pigment;  n,  nerve 

With,  each  OmmatldlUm:    (l)  cornea,  (2)  Crys-  fibers;  nc,  nerve  cells;  r.  retinal 

talline  lens,  or  cone,  (t,)  rhabdom  and  retinula,  pigment;     t,     trachea.— After 

/    \  •  /•    •  1  •        7\       /    \     r  HiCKSON. 

(4)  pigment  {ins  and  rehnal),  (5)  jenestrate 
membrane,  (6)  fibers  of  the  optic  nerve,  (7)  trache<B. 

The  cornea  (Fig.  144)  is  a  biconvex  transparent  portion  of  the  exter- 
nal chitinous  cuticula.  Immediately  beneath  it  are  the  cone  cells,  which 
may  contain  a  clear  fluid  or  else,  as  in  most  insects,  solid  transparent 
cones.  The  rhabdom  is  a  transparent  chitinous  rod  or  a  group  of  rods 
(rhabdomeres)  situated  in  the  long  axis  of  the  ommatidium  and  sur- 
rounded by  greatly  elongated  cells,  which  constitute  the  retinula. 
Two  zones  of  pigment  are  present:  an  outer  zone,  of  iris  pigment,  in 
which  the  pigment  in  the  form  of  fine  black  granules  is  contained 
chiefly  in  short  cells  that  surround  the  retinula  distally;  and  an  inner 
zone,  of  retinal  pigment,  in  which  the  pigment  cells  are  long  and  slender, 
7 


98 


ENTOMOLOGY 


and  enclose  the  retinula  proximally.  All  these 
parts  are  hypodermal  in  origin,  as  is  also  the 
fenestrate  basement  membrane,  through  which 
pass  tracheae  and  nerve  fibers.  The  nerve 
fibrillae,  which  are  ultimate  branches  of  the 
optic  nerve,  pass  into  the  retinal  cells — the 
end-organs  of  vision.  Under  the  basement 
membrane  is  a  fibrous  optic  tract  of  com- 
plex structure. 

Compound  eyes  are  of  three  types:  (i) 
eucone,  in  which  the  cone-cells  form  solid  crys- 
talhne  cones;  (2)  pseudocone,  in  which  the  cone- 
cells  contain  a  transparent  fluid;  and  (3)  acone, 
in  which  there  are  no  cones,  though  the  cone- 
cells  are  present. 

Physiology. — After  much  experimentation 
and  discussion  upon  the  physiology  of  the  com- 
pound eye — the  subject  of  the  monumental 
works  of  Grenacher  and  Exner — Miiller's 
"mosaic"  theory  is  still  generally  accepted, 
though  it  was  proposed  early  in  the  last  cen- 
tury. It  is  thought  that  an  image  is  formed 
by  thousands  of  separate  points  of  light,  each 
of  which  corresponds  to  a  distinct  field  of 
vision  in  the  external  world.  Each  ommati- 
dium  is  adapted  to  transmit  light  along  its  axis 
only  (Fig.  145),  as  oblique  rays  are  lost  by 
absorption  in  the  black  pigment  which  sur- 
rounds the  crystalline  cone  and  the  axial 
rhabdom.  Along  the  rhabdom,  then,  light  can 
reach  and  affect  the  terminations  of  the  optic 
nerve.  Each  ommatidium  does  not  itself  form 
a  picture ;  it  simply  preserves  the  intensity  and 

nucleus;     nv,     nerve    fibrillae;  r     ^       ^^    t       r  •      i 

PC  pseudocone;  pg\  pg\  cells  color  of  the  fight  from  ouc  particular  portion 
containing  iris  pigment;  pg\     f  ^^   ^^^    f  ^-g-^j^  and  whcu  this  is  doue  by 

cell  containing  retinal  pigment ;  '  •' 

r,  one  of  the  six  retinal  cells  hundreds  or  thousands  of  contiguous  ommati- 

which  compose  the  retinula;  Wj,      ,.  .  ,.  ah    ^i      j_    ,i  ■    / 

rhabdom.  composed  of  six  rhab-  dia,  an  image  results.     All  that  the  painter 

domeres;!.  trachea;  <ir.  tracheal    ^J^gg     ^J^q  copieS  an  object,  is  tO  put  together 
vesicle. — After  Hickson.  '  .  ^       .  •'        '  ^  ° 

patches  of  light  in  the  same  relations  of  qual- 
ity and  position  that  he  finds  in  the  object  itself — and  this  is  essen- 


PiG.  144. — Structure  of  an 
ommatidium  of  Calliphora 
vomiloria.  A,  radial  section 
(chiefly);  B,  transverse  sec- 
tion through  middle  region; 
C,  transverse  section  through 
basal  region;  hm,  basement 
membrane;      c,      cornea;      n, 


ANATOMY   AND   PHYSIOLOGY 


99 


tially  what  the  compound  eye  does,  so  far  as  can  be  inferred  from  its 
structure. 

Exner,  removing  the  cones  with  the  corneal  cuticula  (in  Lampyris), 
looked  through  them  from  behind  with  the  aid  of  a  microscope  and 
found  that  the  images  made  by  the  separate  ommatidia  were  either 
very  close  together  or  else  overlapped  one  another,  and  that  in  the 
latter  case  the  details  corresponded;  in  other  words,  as  many  as  twenty 
or  thirty  ommatidia  may  co-operate  to  form  an  image  of  the  same  por- 
tion of  the  field  of  vision;  this  "superposition" 
image  being  correspondingly  bright — an  advan- 
tage, probably,  in  the  case  of  nocturnal  insects. 

Large  convex  eyes  indicate  a  wide  field  of 
xdsion,  while  small  numerous  facets  mean  dis- 
tinctness of  vision,  as  Lubbock  pointed  out.  The 
closer  the  object  the  better  the  sight,  for  the 
greater  will  be  the  number  of  lenses  employed 
to  produce  the  impression,  as  Mollock  says. 
If  Miiller's  theory  is  true,  an  image  may  be 
formed  of  an  object  at  any  reasonable  distance, 
no  power  of  accommodation  being  necessary ; 
while  if,  on  the  other  hand,  each  cornea  with 
its  crystalHne  cones  had  to  form  an  image  after 
the  manner  of  an  ordinary  hand-lens,  only  objects      f'^;    i4S-— Diagram    of 

-'  _         J     ■    J        J  outer  transparent  portion  of 

at  a  definite  distance  could  be  imaged.  an  ommatidiiun  to  illustrate 

The  limit  of  the  perception  of  form  by  insects  ^ay  T^fTnTthf  repeated 

is  placed  at  about  two  meters  for  Law^ym,  i.^o  reflection  and  absorption  of 

./        an  oblique  ray  (5),  which  at 

meters  for  Lepidoptera,  68  centimeters  for  length  emerges  at  c.  p,  iris 
Diptera  and  58  centimeters  for  Hymenoptera.  p^^^^^*- 

It  is  generally  agreed,  however,  that  the  compound  eyes  are  specially 
adapted  to  perceive  movements  of  objects.  The  sensitiveness  of  insects 
to  even  sHght  movements  is  a  matter  of  common  observation;  often, 
however,  these  insects  can  be  picked  up  with  the  fingers,  if  the  operation 
is  performed  slowly  until  the  insect  is  within  the  grasp.  A  moving  object 
affects  different  facets  in  succession,  without  necessitating  any  turning 
of  the  eyes  or  the  head,  as  in  vertebrates.  Furthermore,  on  the  same 
principle,  the  compound  eyes  are  serviceable  for  the  perception  of  form 
when  the  insect  itself  is  moving  rapidly. 

The  arrangement  of  the  pigment  depends  adaptively  upon  the 
quality  of  the  light,  as  Stefanowska  and  Exner  have  shown;  thus,  when 
the  light  is  too  strong,  the  iris  and  retinal  pigment  cells  elongate  around 


lOO  ENTOMOLOGY 

the  ommatidium  and  their  pigment  granules  absorb  from  the  cone 
cells  and  rhabdom  the  excess  of  light.  If  the  light  is  weak,  they  shorten, 
and  absorb  but  a  minimum  amount  of  light.  In  diurnal  insects  the 
pigment  is  adapted  to  absorb  an  excess  of  light;  in  nocturnal  insects, 
on  the  contrary,  it  is  adapted  to  permit  a  maximum  amount  of  light 
to  reach  the  retinal  cells. 

Origin  of  Compound  Eye.- — The  compound  eye  is  often  said  to 
represent  a  group  of  ocelli,  chiefly  for  the  reason  that  externally  there 
appears  to  be  a  transition  from  simple  eyes,  through  agglomerate  eyes, 
to  the  facetted  type.  This  plausible  view,  however,  is  probably  incor- 
rect, for  these  reasons  among  others.  In  the  ocellus,  a  single  lens  serves 
for  all  the  retinulae,  while  in  the  compound  eye  there  are  as  many  lenses 
as  there  are  retinulae.  Moreover,  ocelli  do  not  pass  directly  into  com- 
pound eyes,  but  disappear,  and  the  latter  arise  independently  of  the 
former. 

Probably,  as  Grenacher  holds,  both  the  ocellus  and  the  compound 
eye  are  derived  from  a  common  and  simpler  type  of  eye — are  ''sisters," 
so  to  speak,  derived  from  the  same  parentage. 

Perception  of  Light  through  the  Integument. — In  various  insects, 
as  also  in  earthworms,  blind  chilopods  and  some  other  animals,  light 
affects  the  nervous  system  through  the  general  integument.  Thus 
eyeless  dipterous  larvae  avoid  the  light,  or,  more  precisely,  they  retreat 
from  the  rays  of  shorter  wave-length  (as  the  blue),  but  come  to  rest  in 
the  rays  of  longer  wave-length  (red),  as  if  they  were  in  darkness  (see 
page  307).  The  blind  cave-beetles  of  the  genus  Anophthalmus  react  to 
the  light  of  a  candle  (Packard).  Graber  found  that  a  cockroach  de- 
prived of  its  eyesight  could  stiU  perceive  light,  but  Lubbock  found  that 
an  ant  whose  eyes  had  been  covered  with  an  opaque  varnish  became 
indifferent  to  light. 

Color  Sense. — Insects  undoubtedly  distinguish  certain  colors, 
though  their  color  sense  differs  in  range  from  our  own.  Thus  ants  avoid 
violet  light  as  they  do  sunlight,  but  probably  cannot  distinguish  red  or 
orange  light  from  darkness;  on  the  other  hand,  they  are  extremely 
sensitive  to  the  ultra-violet  rays.  Honey  bees  frequently  select  blue 
flowers:  white  butterflies  (Pieris)  prefer  white  flowers,  and  yellow 
butterflies  (Colias)  appear  to  alight  on  yellow  flowers  in  preference  to 
white  ones  (Packard) .  In  fact,  the  color  sense  is  largely  relied  upon  by 
insects  to  find  particular  flowers  and  by  butterflies  to  a  large  extent  to 
find  their  mates.  To  be  sure,  insects  will  visit  flowers  after  the  brightly 
colored  petals  have  been  removed  or  concealed,  as  Plateau  found,  but 


ANATOMY    AND    PHYSIOLOGY  lOI 

this  does  not  prove  that  the  colors  are  of  no  assistance  to  the  insect, 
though  it  does  show  that  they  are  not  the  sole  attraction — the  odor  also 
being  an  important  guide.  The  honey  bee  is  able  to  distinguish  color 
patterns,  according  to  the  experiments  of  C.  H.  Turner. 

Problematical  Sense  Organs. — As  all  our  ideas  in  regard  to  the 
sensations  of  insects  are  necessarily  inferences  from  our  own  sensory  ex- 
periences, they  are  inevitably  inadequate.  While  it  is  certain  that  in- 
sects have  at  least  the  senses  of  touch,  taste,  smell,  hearing  and  sight,  it 
is  also  certain  that  these  senses  of  theirs  differ  remarkably  in  range  from 
our  own,  as  we  have  shown.  We  can  form  no  accurate  conception  of 
these  ordinary  senses  in  insects,  to  say  nothing  of  others  that  insects 
have,  some  of  which  are  probably  peculiar  to  insects.  Thus  they  have 
many  curious  integumentary  organs  which  from  their  structure  and 
nerve  connections  are  inferred  to  be  sensory  end-organs,  though  their 
functions  are  either  doubtful  or  unknown.  Such  an  organ  is  the  sensil- 
lum  placodeum  (p.  84),  the  use  of  which  is  very  doubtful,  though  the 
organ  is  possibly  affected  by  air  pressure.  Insects  are  extremely  sensi- 
tive to  variations  of  wind,  temperature,  moisture  and  atmospheric 
pressure,  and  very  likely  have  special  end-organs  for  the  perception  of 
these  variations;  indeed,  the  sensilla  trichodea  are  probably  afifected 
by  the  wind,  as  we  have  said. 

The  halteres  of  Diptera,  representing  the  hind  wings,  contain  sensory 
organs  of  some  sort.  They  have  been  variously  regarded  as  olfactory 
(Lee),  auditory  (Graber),  and  as  organs  of  equilibration.  When  one  or 
both  halteres  are  removed,  the  fly  can  no  longer  maintain  its  equilibrium 
in  the  air,  and  Weinland  holds  that  the  direction  of  flight  is  affected  by 
the  movements  of  these  "balancers." 

6.  Digestive  System 

The  alimentary  tract  in  its  simplest  form  is  to  be  seen  in  Thysanura, 
Collembola  and  most  larvae,  in  which  (Fig.  146)  it  is  a  simple  tube  ex- 


FiG.  146. — Alimentary  tract  of  a  collembolan,  Orchesella.  F,  fore  gut;  H,  hind  gut;  M, 
mid  gut;  c,  cardiac  valve;  cm,  circular  muscle;  Im,  longitudinal  muscle;  p,  pharynx;  py, 
pyloric  valve. 


I02  ENTOMOLOGY 

tending  along  the  axis  of  the  body  and  consisting  of  three  regions, 
namely,  fore,  mid  and  hind  gut.  These  regional  distinctions  are  funda- 
mental, as  the  embryology  shows,  for  the  middle  region  is  entodermal 
in  origin  and  the  two  others  are  ectodermal,  as  appears  beyond. 

There  are  many  departures  from  this  primitive  condition,  and  the 
most  specialized  insects  exhibit  the  following  modifications  (Figs.  147, 
148)  of  the  three  primary  regions : 

Fore  intestine  {stomodceum) :  mouth,  pharynx,  oesophagus,  crop,  pro- 
ventriculus  (gizzard),  cardiac  valve. 

Mid  intestine  (mesenteron) :  ventriculus  (stomach) . 

Etind  intestine  (proctodceum) :  pyloric  valve,  ileum,  colon,  rectum, 
anus. 

Stomodaeuni. — The  mouth,  the  anterior  opening  of  the  food  canal, 
is  to  be  distinguished  from  the  pharynx,  a  dilatation  for  the  reception  of 


Fig.  147. — Alimentary  tract  of  a  grasshopper,  Melanoplus  differentialis.  c,  colon;  cr, 
crop;  gc,  gc,  gastric  caeca;  i,  ileum;  m,  mid  intestine,  or  stomach;  mt,  Malpighian,  or  kidney, 
tubes;  o,  oesophagus;  p,  pharynx;  r,  rectum;  s,  salivary  gland  of  left  side. 


food.  In  the  pharynx  of  mandibulate  insects  the  food  is  acted  upon  by 
the  saliva;  in  suctorial  forms  the  pharynx  acts  as  a  pumping  organ,  in 
the  mannei"  already  described. 

The  oesophagus  is  commonly  a  simple  tube  of  small  and  uniform 
caliber,  varying  greatly  in  length  according  to  the  kind  of  insect.  Pass- 
ing between  the  commissures  that  connect  the  brain  with  the  suboeso- 
phageal  gangKon  (Fig.  115),  the  oesophagus  leads  gradually  or  else 
abruptly  into  the  crop  or  gizzard,  or  when  these  are  absent,  directly 
into  the  stomach.  In  addition  to  its  function  of  conducting  food, 
the  oesophagus  is  sometimes  glandular,  as  in  the  grasshopper,  in  which 
it  is  said  to  secrete  the  "molasses"  which  these  insects  emit. 

The  crop  is  conspicuous  in  most  Orthoptera  (Fig.  147)  and  Cole- 
optera  (Fig.  148)  as  a  simple  dilatation.  In  Neuroptera  (Fig.  149)  its 
capacity  is  increased  by  means  of  a  lateral  pocket — the  food  reservoir; 
this  in  Lepidoptera,  Hymenoptera  and  Diptera  is  a  sac  (Fig.  150,  c) 
communicating  with  the  oesophagus  by  means  of  a  short  neck  or  a 


ANATOMY   AND   PHYSIOLOGY 


103 


long  tube,  and  serving  as  a  temporary  receptacle  for  food.  In  herbiv- 
orous insects  the  crop  contains  glucose  formed  from  starch  by  the 
action  of  saliva  or  by  the  secretion  of  the  crop  itself;  in  carnivorous 
insects  this  secretion  converts  albuminoids  into  assimilable  peptone- 
like substances. 


Next   comes   the    enlargement 


known  as  the  proventriculus,  or 
gizzard,  which  is  present  in  many 
insects,  especially  Orthoptera  and 
Coleoptera  (Fig.  148),  and  is 
usually  found  in  such  mandibulate 
insects  as  feed  upon  hard  sub- 
stances.    The   proventriculus  is 


Fig.  148. — Digestive  system  of  a  beetle, 
Carabus.  a,  anal  gland;  c  (of  fore  gut),  crop; 
c  (of  hind  gut),  colon,  merging  into  rectum; 
d,  evacuating  duct  of  anal  gland;  g,  gastric 
caeca;  i,  ileum;  m,  mid  intestine;  mt,  Mal- 
pighian  tubes;  o,  oesophagus;  p,  proventricu- 
lus; r,  reservoir. — After  Kolbe. 


Pig.  149. — Digestive  system  of  Myrme- 
leon  larva,  c,  caecum;  cr,  crop;  m,  mid 
intestine;  mt,  Malpighian  tubes;  s,  spin- 
neret.— After  Meinert. 


lined  with  chitinous  teeth  or  ridges  for  straining  the  food,  and  has  power- 
ful circular  muscles  to  squeeze  the  food  back  into  the  stomach,  as  well  as 
longitudinal  m.uscles  for  relaxing,  or  opening,  the  gizzard.  The  pro- 
ventriculus not  only  serves  as  a  strainer,  but  also  helps  to  comminute 
the  food,  like  the  gizzard  of  a  bird. 


I04 


ENTOMOLOGY 


In  most  insects  a  cardiac  valve  guajrds  the  entrance  to  the  stomach, 
preventing  the  return  of  food  to  the  gullet.     This  valve  (Figs.  146,  151) 


'  cm 

Fig.  150. — Alimentary  tract  of  a  moth.  Sphinx,  c,  food  reservoir;  cl,  colon;  cm, 
cascum;  i,  ileum;  m,  mid  intestine;  mt,  Malpighian  tubes;  o,  oesophagus;  r,  rectum;  s,  salivary 
gland. — After  Wagner. 

is  an  intrusion  of  the  stomodaeum  into  the  mesenteron,  forming  a  circu- 
lar lip  which  permits  food  to  pass  backward,  but  closes  upon  pressure 
from  behind. 

Mesenteron. — The  ventriculus,  otherwise  known  as  the  mid  intestine, 
or  stomach,  is  usually  a  simple  tube  of  large  caliber, 
as  compared  with  the  oesophagus  or  intestine,  and  into 
the  ventriculus  may  open  glandular  blind  tubes,  or 
gastric  ccBca  (Figs.  147,  148) ;  these,  though  numerous 
in  some  insects,  are  commonly  few  in  number  and 
restricted  to  the  anterior  region  of  the  stomach.  The 
gastric  caeca  of  Orthoptera  secrete  a  weak  acid  which 
emulsifies  fats,  or  one  which  pa,sses  forward  into  the 
crop,  there  to  act  upon  albuminoid  substances.  In 
the  stomach  the  food  may  be  acted  upon  by  a  fluid 
secreted  by  specialized  cells  of  the  epithehal  wall. 
In  various  insects,  certain  cells  project  periodically 
into  the  lumen  of  the  stomach  as  papillae,  which  by  a 
_  process  of  constriction  become   separated  from  the 

valve  of  young  muscid  parent  cells  and  mix  bodily  with  the  food.  Thisphe- 
/.^^provekScJiu^s^^^i  nomenon  takes  place  in  the  larva  oiPtychoptera  (van 
valve.     In  an  older  Gchuchten),  also  in  nymphs  of  Odonata  (Necdham), 

larva   the  valve  pro-  i     i  i         r       •  i  i 

jects  into  the  mid  in-  and  IS  probably  of  widespread  occurrence  among  m- 
I.evsky7'^^'''^°'^^"  sects-  The  chief  function  of  the  stomach  is  absorp- 
tion, which  is  effected  by  the  general  epithelium. 
Physiologically,  the  so-called  stomach  of  an  insect  is  quite  unlike  the 
stomach  of  a  vertebrate,  being  more  like  an  intestine. 

Proctodaeum. — At  the  anterior  end  of  the  hind  intestine  there  is 
usually  a  pyloric  valve,  which  prevents  the  contents  of  the  intestine 


ANATOMY   AND    PHYSIOLOGY 


f05 


from  returning  into  the  stomach.  This  valve  may  operate  by  means  of 
a  sphincter,  or  constricting,  muscle,  or  may,  as  in  Collembola  (Fig.  146), 
consist  of  a  backward-projecting  circular  ridge,  or  lip,  which  closes 
upon  pressure  from  behind. 

In  its  primitive  condition  the  hind  intestine  is  a  simple  tube  (Fig. 
146).  Usually,  however,  it  presents  two  or  even  three  specialized 
regions,  namely  and  in  order,  ileum,  colon  and  rectum  (Fig.  147).  The 
hind  intestine  varies  greatly  in  length  and  is  frequently  so  long  as  to  be 
thrown  into  convolutions  (Fig.  152).  The  ileum  is  short  and  stout  in 
grasshoppers  (Fig.  147);  long,  slender  and  convoluted  in  many  carniv- 


/'r^^ 


Pig.  152. — Digestive  system  of  Belos- 
toma.  c,  caecum;  I,  ileum;  w,  mid  intestine; 
mt,  Malpighian  tubes;  r,  salivary  reservoir; 
5,  salivary  gland. — After  LocY,  from  the 
American  Naturalist. 


Fig.  153. — Wall  of  mid  intestine  of  silk- 
worm, transverse  section,  b,  basement  mem- 
brane; c,  circular  muscle;  /,  intima;  I,  longi- 
tudinal muscle;  n,  n,  nuclei  of  epithelial 
cells;  5,  secretory  cell. 


orous  beetles;  and  quite  short  in  caterpillars  and  most  other  larvae;  its 
function  is  absorption.  The  colon,  often  absent,  is  evident  in  Orthop- 
tera  and  Lepidoptera  and  may  bear  {Benacus,  Dytiscus,  Silphidse, 
Lepidoptera)  a  conspicuous  caecal  appendage  (Figs.  150,  152)  of  doubt- 
ful function,  though  possibly  a  reservoir  for  excretions.  The  colon 
contains  indigestible  matter  and  the  waste  products  of  digestion,  includ- 
ing the  excretions  of  the  Malpighian  tubes.  The  rectum  (Fig.  147)  is 
thick-walled,  strongly  muscular  and  often  folded  internally.  Its 
office  is  to  expel  excrementitious  matter,  consisting  largely  of  the  indi- 
gestible substances  chitin,  cellulose  and  chlorophyll.  The  rectum 
terminates  in  the  anus,  which  opens  through  the  last  segment  of  the 
abdomen,  always  above  the  genital  aperture. 


io6 


ENTOMOLOGY 


g 


Histology. — The  epithelial  wall  of  the  alimentary  tract  is  a  single 
layer  of  cells  (Fig.  153),  which  secretes  the  intima,  or  lining  layer,  and 
the  basement  membrane — a  delicate,  structureless  enveloping  layer. 
The  intima,  which  is  continuous  with  the  external  cuticula,  is  chitinous 
in  the  fore  and  hind  gut  (which  are  ectodermal  in  origin) ,  but  not  in  the 
mid  gut  (entodermal) ,  and  usually  exhibits  extremely  fine  transverse 
striae,  which  are  due  probably  to  minute  pore  canals.  Surrounding 
the  basement  membrane  is  a  series  of  circular  muscles  and  outside  these 
is  a  layer  of  longitudinal  muscles  in  the  mid  gut.  In 
the  fore  gut  the  longitudinal  muscles  are  frequently 
under  the  circular  muscles;  and  in  the  hind  gut  there 
may  be  two  layers  of  circular  muscles  with  longitudinal 
muscles  running  between  them;  but  there  are  many 
variations  in  the  relative  positions  of  the  two  kinds  of 
muscles  in  different  kinds  of  insects.  The  circular 
muscles  serve  to  constrict  the  pharynx  in  sucking  insects 
and,  in  general,  to  squeeze  backward  the  contents  of  the 
alimentary  canal  by  successively  reducing  its  caliber. 
The  longitudinal  muscles,  restricted  almost  entirely  to 
the  mid  intestine,  act  in  opposition  to  the  constricting 
muscles  to  enlarge  the  lumen  of  the  food  canal  and  in 
addition  to  effect  peristaltic  movements  of  the  stomach. 
The  intima  of  the  crop  is  sometimes  shaped  into 
teeth,  and  that  of  the  proventricvilus  is  heavily  chitin- 
ized  and  variously  modified  to  form  spines,  teeth  or 
ridges, 

Peritrophic  Membrane. — This  membrane  forms 
an  elastic  tube  inside  the  mid  intestine  and  hind  in- 
testine; is  derived    usually  from  the   epithelial   cells 
of   the  mesenteron;  and  is,  in  some  instances  at  least, 
renewed    periodically.     The    peritrophic   membrane, 
found  in  ants,  wasps,  caterpillars,  and  larvae  and  adults 
of  many  beetles,  etc.,  is  characteristic  of  insects  that  consume  solid  food 
containing  much  hard,  indigestible  matter,  and  doubtless  serves  to  pro- 
tect the  epithelium  of  the  mid  intestine  from  mechanical  injury. 

Salivary  Glands. — In  their  simplest  condition,  the  salivary  glands 
are  a  pair  of  blind  tubes  (Fig.  154),  one  on  each  side  of  the  oesophagus 
and  opening  separately  at  the  base  of  the  hypopharynx.  Commonly, 
however,  the  glands  open  through  two  salivary  ducts  into  a  common, 
or  evacuating,  duct;  a  pair  of  salivary  reservoirs  (Fig.  155)  may  be 


Fig.  154. — A  sim- 
ple salivary  gland  of 
CcBcilius.  c,  canal;  d, 
duct;  g,  g,  glandular 
cells. — After  Kolbe. 


ANATOMY   AND   PHYSIOLOGY 


107 


present  and  the  glands  are  frequently  branched  or  lobed,  and  though 
usually  confined  to  the  head,  may  extend  into  the  thorax  or  even  into 
the  abdomen.  • 

Many  insects  have  more  than  one  pair  of  glands  opening  into  the 
pharynx  or  oesophagus ;  thus  the  honey  bee  has  six  pairs  and  Hymenop- 


.,  b 


-  B. 


Fig.   155. — Right  salivary  gland  of  cockroach,  ventral 
aspect,     c,  common  duct;  g,  gland;  h,  hypopharynx;  r, 
-After  MiALL  and  Denny. 


reservoir.- 


FiG.  156. — Histology  of 
salivary  gland  of  Ccecilius, 
radial  section,  b,  basement 
membrane;  c,  canal;  g,  g, 
glandular  cell;  i,  intima;  n, 
nucleus. — After  Kolbe. 

tera  as  a  whole  have  as  many  as  ten  different  pairs.  Though  all  these 
are  loosely  spoken  of  as  salivary  glands,  it  is  better  to  restrict  that 
term  to  the  pair  of  glands  that  open  at  the  hypopharynx. 

All  these  cephalic  glands  are  evaginations  of  the  stomodaeum  (ecto- 
dermal in  origin)  and  consist  of  an  epithelial  layer  with  the  customary 
intima  and  basement  membrane  (Fig.  156).  The  nuclei  are  large,  as  is 
usually  the  case  in  glandular  cells,  and 
the  cytoplasm  consists  of  a  dense 
framework  (appearing  in  sections  as  a 
network)  enclosing  vacuoles  of  a  clear 
substanc^the secretion;  the  chitinous     ,P'^-   ^s 7. -One  of  the  three-iobed 

'  salivary    glands    of    a  mosquito.     The 

intima  is  penetrated  by  fine  pore  canals  middle  lobe  secretes  the  poison.— After 

,1  1  1  •   1      ,1  .•  Macloskie,    from    the    American  Nat- 

through  which   the  secretion  passes,  uraiist. 

In  many  insects,  notably  the  cockroach, 

the  common  duct  is  held  distended  by  spiral  threads  which  give  the  duct 

much  the  appearance  of  a  trachea. 

In  herbivorous  insects  the  saliva  changes  starch  into  glucose,  as  in 
vertebrates;  in  carnivorous  forms  it  acts  on  proteids  and  is  often  used 
to  poison  the  prey,  as  in  the  larva  of  Dytiscus.  In  the  mosquito  each 
gland  is  three-lobed  (Fig.  157) ;  the  middle  lobe  is  different  in  appearance 
from  the  two  others  and  secretes  a  poisonous  fluid  which  is  carried  out 


io8 


ENTOMOLOGY 


along  the  hypopharynx.  Though  this  poison  is  said  to  faciHtate  the 
process  of  blood-sucking  by  preventing  the  coagulation  of  the  blood,  its 
primary  use  was  perhaps  to  pre\»ent  the  coagulation  of  proteids  in  the 
juices  of  plants. 

Malpighian  Tubes. — The  kidney,  or  Malpighian,  tubes,  present  in 
nearly  all  insects,  are  long,  slender,  blind  tubes  opening  into  the  intestine 
immediately  behind  the  stomach  as  a  rule  (Figs 
147, 148) ,  but  always  into  the  intestine.  The  num- 
ber of  kidney  tubes  is  very  different  in  different  in- 
sects; Collembola  have  none,  while  Odonata  have 
fifty  or  more  and  Locustidae  as  many  as  one  hun- 
dred and  fifty;  commonly,  however,  there  are  four 
or  six,  in  Coleoptera,  Lepidoptera  and  many  other 


Fig.       158. — Portion  Pig.   159. — Cross-section    of    Malpighian   tube   of   silkworm 

of    Malpighian   tube  of  Bombyx   tnori.      b,    basement  membrane;   c,  crystals;  1,  intima 

caterpillar,     Samia    ce-  I,  lumen;  n,  nucleus;  p,  peritoneal  layer.     Greatly  magnified. 
cropia,    surface  view. 

orders.  Not  more  than  six  and  frequently  only  four  occur  in  the 
embryo  (Wheeler),  though  these  few  embryonic  tubes  may  subsequently 
branch  into  many. 

The  Malpighian  tubes  (Fig.  158)  are  evaginations  of  the  proctodaeum 
and  are  consequently  ectodermal.  A  cross-section  of  a  tube  shows  a 
ring  of  from  one  to  six  or  more  large  polygonal  cells  (Fig.  159),  which 
often  project  into  the  lumen  of  the  tube;  the  nuclei  are  usually  large  and 
may  be  branched,  as  in  Lepidoptera.  A  chitinous  intima,  traversed  by 
pore  canals,  lines  the  tube,  and  a  delicate  basement  membrane  is  present, 
surrounded  by  a  peritoneal  layer  of  connective  tissue.  Furthermore, 
the  urinary  tubes  are  richly  supplied  with  tracheae.  In  function,  the 
Malpighian  tubes  are  analogous  to  the  vertebrate  kidneys  and  con- 
tain a  great  variety  of  substances,  chief  among  which  are  uric  acid  and  its 
derivatives  (such  as  urate  of  sodium  and  of  ammonium),  calcium  oxalate 
and  calcium  carbonate. 


ANATOMY   AND   PHYSIOLOGY 


109 


Parts  of  the  fat-body  may  also  be  concerned  in  excretion;  thus  the 
fat-body  in  CoUembola  and  Orthoptera  serves  for  the  permanent  storage 
of  urates. 

7.  Circulatory  System 

Insects,  unlike  vertebrates,  have  no  system  of  closed  blood-vessels, 
but  the  blood  wanders  freely  through  the  body 
cavity  to  enter  eventually  the  dorsal  vessel,  which 
resembles  a  heart  merely  in  being  a  propulsatory 
organ. 

Dorsal  Vessel. — The  dorsal  vessel  (Figs.  160, 
164)  is  a  delicate  tube  extending  along  the  median 
dorsal  line  immediately  under  the  integument. 
A  simple  tube  in  some  larvae,  it  consists  in  most 
adults  chiefly  of  a  series  of  chambers,  each  of-  which 
has  on  each  side  a  valvular  opening,  or  ostium 
(Fig.  161),  which  permits  the  ingress  of  blood  but 
opposes  its  egress;  within  the  chambers  occur 
other  valvular  folds  that  allow  the  blood  to  move 
forward  only.  With  few  exceptions  (Ephemeridae) 
the  dorsal  vessel  is  blind  behind  and  the  blood  can 
enter  it  only  through  the  lateral  ostia. 

Aorta. — The  posterior,  or  pulsating  portion 
{heart)  of  the  dorsal  vessel  is  confined  for  the  most 
part  to  the  abdomen;  the  anterior  portion,  or  aorta, 
extends  as  a  simple  attenuated  tube  through  the 
thorax  and  into  the  head,  where  it  passes  under 
the  brain  and  usually  divides  into  two  branches  gel  of  beetk.^LMcanws.^^^ 
(Fig.  164),  each  of  which  may  again  branch.     In  ^o"^*^:  «^'  ^^^^y  muscle;  o. 

\      ,         7  ,  ,        1  1  1  1  1  1    ostium.— After        Straus- 

the  head  the  blood  leaves  the  aorta  abruptly  and  Durckheim. 
enters  the  general  body  cavity; 

Alary  Muscles. — Extending  outward  from  the  "heart,"  or  pro- 
pulsatory  portion,  and  making  with  the  dorsal  wall  of  the  body  a  pericar- 
dial chamber,  is  a  loose  diaphragm,  formed  largely  by  paired  fan-like 
muscles — the  alary  muscles  (Figs.  160,  162).  These  are  thought  to  assist 
the  heart  in  its  propulsatory  action. 

Structure  of  the  Heart.— The  wall  of  the  heart  is  remarkably  thin, 
and  consists  essentially  of  a  muscular  layer  containing  closely-set  circular 
or  spiral  fibers  and  separated  longitudinal  fibers,  with  scattered  nucle- 
ated cells  among  the  fibers.     This  muscular  tube  is  between  two  layers: 


aio 


ENTOMOLOGY 


ail  inner  membrane,  or  sarcolemma,  and  an  outer  layer  of  elastic  con- 
nective tissue,  the  adventitia. 

Pericardial  Cells.  Nephrocytes. — The  pericardial  cells  occur  gener- 
ally in  larvae  and  imagines  in  the  vicinity  of  the  heart,  usually  on  each 
side  of  the  heart,  and  arranged  frequently  in  longitudinal  "garland-like" 


Fig.  i6i. — Diagram  of  a  portion  of  the 
heart  of  a  dragon  fly  nymph,  Epilheca. 
o,  ostium;  v,  valve;  the  arrows  indicate 
the  course  of  the  blood. — After  Kolbe. 


Fig.  162. — Diagrammatic  cross-section  of 
pericardial  region  of  a  grasshopper,  CEdipoda. 
a,  alary  muscle;  d,  dorsal  vessel;  s,  suspensory 
muscles;  sp,  septum. — After  Graber. 


series.  They  vary  greatly  in  position,  number,  form,  size  and  contents, 
and  evidently  bear  some  relation  to  the  circulatory  system;  though 
many  functions  have  been  assigned  to  them.  In  allusion  to  their 
supposed  excretory  function,  these  cells  have  been  named  nephrocytes, 
the  term  applying  particularly  to  such  cells  as  select  and  absorb  acid 
ammonia  carmine,  when  that  stain  is  injected  into  the  living  insect. 

Ventral  Sinus.— In  many  if  not  most  insects  a  pulsatory  septum 
(Fig.  180,  v)  extends  across  the  floor  of  the  body  cavity  to  form  a  sinus, 


Fig.  163. — Blood  corpuscles  of  a  grasshopper,  Slenobothrus.  a-f,  corpuscles  covered 
with  fat-globules;  g,  corpuscle  after  treatment  with  glycerine,  showing  nucleus. — After 
Graber. 

in  which  the  blood  flows  backward,  bathing  the  ventral  nerve  cord  as  it 
goes.  This  ventral  sinus  supplements  the  heart  in  a  minor  way,  as  do 
also  the  local  pulsatory  sacs  which  have  been  discovered  in  the  legs 
of  aquatic  Hemiptera  and  the  head  of  Orthoptera. 

Blood. — The  blood,  or  hcemolymph,  of  an  insect  consists  chiefly  of  a 
watery  fluid,  or  plasma,  which  contains  corpuscles  or  leucocytes.     Though 


ANATOMY    AND    PHYSIOLOGY 


usually  colorless,  the  plasma  is  sometimes  yellow  (Coccinellidae, 
Meloidae),  often  greenish  in  herbivorous  insects  from  the  presence  of 
chlorophyll,  and  sometimes  of  other  colors;  often  the  blood  owes  its 
hue  to  yellow  or  red  drops  of  fat  on  the  surface  of  the  blood  corpuscles 
Fig.  163). 

Haemocytes. — The  corpuscles  or  hcBmocytes  {leucocytes)  are  minute 
nucleated  cells,  6  to  30  /x  in  diameter,  variable  in  form  even  in  the  same 
species,  but  commonly  (Fig.  163)  round,  oval  or  ovate  in  outline, 
though  often  disk-shaped,  elongate  or  amoeboid  in  form. 

Function  of  the  Blood. — The  blood 
of  insects  contains  many  substances, 
including  egg  albumin,  globulin,  fibrin, 
iron,  potassium  and  sodium  (Mayer), 
and  especially  such  a  large  amount  of 
fatty  material  that  its  principal  function 
is  probably  one  of  nutrition;  the  blood 
of  an  insect  contains  no  red  corpuscles 
and  has  little  or  nothing  to  do  with  the 
aeration  of  tissues,  that  function  being 
relegated  to  the  tracheal  system. 

Circulation.— The  course  of  the  cir- 
culation is  evident  in  transparent  aquatic 
nymphs  or  larvae.  In  odonate  or  ephe- 
merid  nymphs,  currents  of  blood  may  be 
seen  (Fig.  164)  flowing  through  the  spaces 
between  muscles,  tracheae,  nerves,  etc., 
and   bathing   all   the  tissues;  separate      Fig-  164.— Diagram  to  indicate  the 

.  course  of  the  blood  in  the  nymph  of  a 

outgomg  and  mcommg  streams  may  be  dragon    fly,    Epitheca.    a,  aorta;    h. 

distinguished  in  the  antenna  and  legs;    heart;  the  arrows  show  directions  taken 
°  °    '    by  currents  of  blood. — After  Kolbe. 

the  returning  blood  flows  along  the  sides 

of  the  body  and  through  the  ventral  sinus  and  the  pericardial  chamber, 
eventually  to  enter  the  lateral  ostia  of  the  dorsal  vessel.  A  circulation 
of  blood  occurs  in  the  wings  of  freshly  emerged  Odonata,  Ephemerida, 
Coleoptera,  Lepidoptera,  etc.,  the  currents  trending  along  the  tracheae; 
this  circulation  ceases,  however,  with  the  drying  of  the  wings. 

The  chambers  of  the  dorsal  vessel  expand  and  contract  successively 
from  behind  forward.  At  the  expansion  (diastole)  of  a  chamber  its  ostia 
open  and  admit  blood;  at  contraction  (systole)  the  ostia  close,  as  well  as 
the  valve  of  the  chamber  next  behind,  while  the  chamber  next  in  front 
expands,  affording  the  only  exit  for  the  blood.  The  valves  close  partly 
through  blood-pressure  and  partly  by  muscular  action. 


112  ENTOMOLOGY 

The  rate  of  pulsation  depends  to  a  great  extent  upon  the  activity  of 
the  insect  and  upon  the  temperature  and  the  amount  of  oxygen  or  car- 
bonic acid  gas  in  the  surrounding  atmosphere.  Oxygen  accelerates  the 
action  of  the  heart  and  carbonic  acid  gas  retards  it.  A  decrease  of  8°  or 
io°  C.  in  the  case  of  the  silkworm  lowers  the  number  of  beats  from  30  or 
40  to  6  or  8  per  minute.  The  more  active  an  insect,  the  faster  its  heart 
beats. 

The  rate  of  pulsation  is  very  different  in  the  different  stages  of  the 
same  insect.  Thus  in  Sphinx  ligustri,  according  to  Newport,  the  mean 
number  of  pulsations  in  a  moderately  active  larva  before  the  first  molt 
is  about  82  or  83  per  minute;  before  the  second  molt,  89,  sinking  to  63 
before  the  third  molt,  to  45  before  the  fourth,  and  to  39  in  the  final 
larval  stage;  but  the  force  of  the  circulation  increases  as  the  pulsations 
decrease  in  number.  During  the  quiescent  period  immediately  preced- 
ing each  molt,  the  number  of  beats  is  about  30.  In  the  pupal  stage 
the  number  sinks  to  22,  and  then  lowers  until,  during  winter,  the  pulsa- 
tions almost  cease.  The  moth  in  repose  shows  41  to  50  per  minute,  and 
after  flight  as  many  as  139. 

8.  Fat-Body 

The  fat-body  appears  (Fig.  165)  as  many-lobed  masses  of  tissue  filling 
in  spaces  between  other  organs  and  occupying  a  large  part  of  the  body 
cavity.  The  distribution  of  the  fat-body  is  to  a  certain  extent  definite, 
however,  for  the  fat-tissue  conforms  to  the  general  segmentation  and  is 
arranged  in  each  segment  with  an  approach  to  symmetry.  Much  of 
this  tissue  forms  a  distinct  peripheral  layer  in  each  segment,  and  masses 
of  fat-body  occur  constantly  on  each  side  of  the  alimentary  tract  and 
also  at  the  sides  of  the  dorsal  vessel,  in  the  latter  case  forming  the 
pericardial  fat-body. 

Fat-Cells. — The  fat-cells  (Fig.  166)  are  large  and  at  first  more  or 
less  spherical,  with  a  single  nucleus  (though  there  are  said  to  be  two  in 
Apis  and  several  in  Musca),  but  the  cellular  structure  of  the  fat- tissue  is 
often  difficult  to  make  out  because  the  cells  are  usually  filled  with  glob- 
ules of  fat  (Fig.  167),  while  old  cells  break  down,  leaving  only  a  disorderly 
network.  The  fat-cells  sometimes  contain  an  albuminoid  substance,  and 
usually  the  fat-body  includes  considerable  quantities  of  uric  acid  or  its 
derivatives,  frequently  in  the  form  of  conspicuous  concretions. 

Functions. — The  physiology  of  the  fat-system  is  still  obscure. 
Probably  the  fat-body  combines  several  functions.  In  caterpillars  and 
other  larvae  it  furnishes  a  reserve  supply  of  nutriment,  at  the  expense  of 


ANATOMY    AND   PHYSIOLOGY 


113 


Fig.  165. — Transverse  section  of  the  abdomen  of  a  caterpillar,  Pieris  rapm.  b,  blood  cor- 
puscles; c,  cuticula;  d,  dorsal  vessel;  /,  fat-body;  g.  ganglion;  h,  hypodermis;  I.  leg;w, 
muscle;  mi,  mid  intestine,  containing  fragments  of  cabbage  leaves;  mt,  Malpighian  tube;  s, 
silk  gland;  sp,  spiracle;  tr,  trachea. 

which  the  metamorphosis  takes  place;  the  amount  of  fat  increases  as 
the  larva  grows,  and  diminishes  in  the  pupal  stage,  though  some  of  it 
lasts  over  to  furnish  nourishment  for  the 
imago  and  its  germ  cells.     The  gradual 
accumulation  of  uric  acid  and  urates  in 
the  fat-body  indicates  an  excretory  func- 
tion, particularly  in  Collembola,   which 
have  no  Malpighian  tubes.    The  intimate      ^^^    i66.-Fat-ceiis  of  a  eater- 
association  between  the  ultimate  tracheal  pillar,  Pieris.    a,   cells  filled  with 

,      ,       r    .   ^       11         1    J  drops  of  fat;  5,  cell  freed  of  fat-drops, 

branches  and  the  fat-body  has  led  some  showing  nucleus.— After  Kolbe. 
authorities  to  ascribe  a  respiratory  func- 
tion  to   the   latter.     A   close   relation   of    some    sort    exists  also  be- 
tween the  fat-system   and  the  blood-system;  fat-cells  are  found  free 
in  the  blood,  and  the   blood  corpuscles  originate  in   the  thorax  and 


114 


ENTOMOLOGY 


abdomen  from  tissues  that  can  scarcely  be  distinguished  from  fat- 
tissues.  The  corpuscles  {leucocytes,  or  phagocytes)  which  in  some  insects 
absorb  effete  larval  tissues  during  metamorphosis  have  been  by  some 
authors  regarded  as  wandering  fat-cells.  Cells  constituting  the  peri- 
cardial fat-body  are  attached  to  the 
lateral  muscles  {alary  muscles)  of  the 
dorsal  vessel,  but  almost  nothing  is 
definitely  known  as  to  their  function. 
CEnocytes. — Associated  with  the 
fat-body  proper  and  with  tracheae  as 
well  are  the  peculiar  yellow  cells  known 
as  cenocytes  (Fig.  i68),  that  occur  in 
abdominal  segments  of  larvae.  These 
cells  are  enormous  in  size  as  compared 
with  all  other  insect-cellsexceptingova, 
and  are  essentially  isolated  from  one 
Fig.  167.— Section  through  fat-body  of  a  another,  though  grouped  among  tra- 
siikworm.  showing  nucleated  cells,  loaded  cheal  branches  into  loosc  clusters,  One  on 

with  drops  of  fat. 

each  side  of  a  spiracle-bearing  segment. 

After  arising  from  the  primitive  ectoderm  the  cenocytes  never  divide, 
but  gradually  increase  in  size  (Wheeler),  and  their  size  is  in  a  general  way 
proportional  to  that  of  the  fat-body. 

Their  function  has  been  problematical  until  recently.  Many  ob- 
servers have  regarded  them  as  ductless  glands,  having  seen  "microscop- 
ical exudations  around  the  periphery  of  the  cytoplasm, 
especially  at  times  when  the  nucleus  is  greatly  rami- 
fied, and  therefore  manifesting  its  great  activity" 
(Glaser). 

R.  W.  Glaser  has  thrown  light  upon  the  nature  of 
the  oenocytic  fluid.  By  using  three-year-old  caterpillars 
of  the  leopard  moth,  Zeuzera  pyrina,  which  have  a 
great  amount  of  fatty  tissue  and  correspondingly  large 
cenocytes,  he  was  able  to  extract  enough  of  the  fluid 
for  chemical  experiments.     He  found  by  carefully  con-      ^^^-   168.— CEno- 

-^  -^  cytes     and     accom- 

ducted  tests  that  the  fluid  had  the  power  of  oxidizing  panying      tracheae, 
fats,  by  means  of  enzymes  known  as  oxidases  (though  siik^o^.^"^^'^  °^  ^ 
no  fat-splitting  enzyme,  or  lipase,  was  present),  and 
concluded  that  the  secretion  of  the  cenocytes  is  used  to  oxidize  the 
reserve  food  stored  up  by  the  larva  in  the  form  of  fat. 

Photogeny. — This  phenomenon  appears  sporadically  and  by  various 
means  in  protozoans,  worms,  insects,  fishes  and  other  animals.     Lumi- 


ANATOMY    AND    PHYSIOLOGY  115 

nosity  in  insects,  though  sometimes  merely  an  incidental  and  pathologi- 
cal effect  of  bacteria,  is  usually  produced  by  special  organs  in  which 
hght  is  generated,  probably  by  the  oxidation  of  a  fatty  substance. 

There  are  not  many  luminous  insects.  Those  best  known  are  the 
Mexican  and  West  Indian  beetles  of  the  genus  Pyrophorus  (Elateridse) , 
in  which  the  pronotum  bears  a  pair  of  luminous  spots,  and  the  common 
fireflies  (Lampyrid^).  In  Lampyridae  the  light  is  emitted  from  the 
ventral  side  of  the  posterior  abdominal  segments,  and  the  structure  of 
the  photogenic  organ  is  essentially  the  same  throughout  the  family. 
In  Photinus  this  organ  (Fig.  169)  consists  of  two  layers;  a  ventral  photo- 
genic layer  and  a  dorsal  reflecting  layer.  The  latter,  white  and  opaque, 
consists  of  polygonal  cells  containing  large  quantities  of  crystals  of  ur- 
ates; the  former  layer  is  composed 
of  tracheal  structures  and  inter- 
vening parenchyma  cells.  The 
tracheae  branch  profusely  in  the 
photogenic  layer,  where  the  larger 
air-tubes  are  each  surrounded  by 
a  more  or  less  cylindrical  mass  of 
cells;  tracheal  branches  penetrate 
between  the  cells  of  each  cylinder, 
at  the  edge  of  which  they  pass  into 
tracheoles   which   penetrate   the  ^ 

photogenic  tissue  and  anastomose         ^^^     ,69.-Transverse  section  of  portion  of 

with  those  of  adjacent  cylinders;    photogenic    organ    of    a    firefly,   Photinus.     c, 

1  c   A-\^      4.   „„V,^^lo,.    cylinder;^,  photogeniclayer;*-,  reflecting  layer; 

in  the  meshes  of  the  tracheolar  ^/trachekf— After  Townsend. 
network  is  agranular  substance  of 

fatty  nature  ("differentiated  fat-body"),  the  oxidation  of  which  is  the 
source  of  the  luminosity,  it  is  inferred.  The  photogenic  tissues  of 
Photinus,  after  being  dried  and  kept  in  sealed  tubes,  have  retained  their 
photogenic  power  for  more  than  eighteen  months,  glowing  after  this 
interval  upon  the  "  application  of  water  in  the  presence  of  air  or  oxygen  " 
(McDermott).  Three  factors  are  involved  in  the  production  of  the 
light:  a  substance  to  be  oxidized,  oxygen  and  water. 

Professor  W.  E.  Burge  has  found  that  the  catalase  content  of  a 
luminous  insect  where  oxidation  is  presumably  more  intense  is  greater 
than  that  of  a  non-luminous  insect  where  oxidation  is  less  intense. 

The  rays  emitted  by  the  common  fireflies  are  remarkable  in  being 
almost  entirely  light  rays.  According  to  Young  and  Langley,  the  radia- 
tions of  an  ordinary  gas-flame  contain  less  than  three  per  cent,  of  visible 


Il6  ENTOMOLOGY 

rays,  the  remainder  being  heat  or  chemical  rays,  of  no  value  for  illumina- 
ting purposes;  while  the  light-giving  efficiency  of  the  electric  arc  is  only 
ten  per  cent,  and  that  of  sunhght  only  thirty-five  per  cent.  The  luminous 
efficiency  of  the  firefly  is,  however,  not  much  under  one  hundred  per 
cent.;  in  Photuris  pennsylvanica  it  is  about  ninety-two  per  cent.,  accord- 
ing to  Coblentz — an  efficiency  as  yet  unapproached  by  artificial  means. 
The  actinic  power  of  the  light  is  so  slight  that  it  affects  a  photographic 
plate  only  after  a  long  exposure.  .  Coblentz,  who  has  applied  most 
refined  methods  of  measurement  to  the  radiation  of  fireflies,  found 
that  exposures  of  one  to  five  hours  were  necessary  with  the  spectro- 
graph. He  was  unable  to  detect  any  infra-red  radiation;  the  thermal 
radiation,  if  present,  being  immeasurably  small  as  yet.  The  intensity 
of  the  glow  averages  3'^o>ooo  candle  power  in  our  common  fireflies, 
according  to  Coblentz. 

This  luminosity  serves  to  bring  the  sexes  together.  "The  male  flies 
over  the  tops  of  the  grasses,  weeds,  etc.,  dropping  down  between  them 
and  flashing;  any  females  that  come  within  the  range  of  his  flash,  answer 
by  their  slower  flash;  if  the  male  sees  this  answering  flash  from  one,  he 
approaches  her,  flashes  again,  to  which  she  answers,  and  he  then  finally 
locates  her  definitely  by  means  of  subsequent  flashes,"  as  McDermott 
says.  He  found  that  he  coifld  get  responses  from  the  females  by  imi- 
tating the  flash  of  the  male  with  a  small  electric  bulb  or  even  with  a  com- 
mon safety  match,  and  that  he  could  deceive  the  males  also  by  flashing 
the  tiny  electric  fight  after  the  manner  of  the  female. 

Synchronism. — Several  observers  in  the  PhiHppines  and  East 
Indies  have  seen  the  phenomenon  of  thousands  of  fireflies  flashing 
exactly  in  unison;  all  the  fireflies  in  the  same  tree,  for  example, flashing 
simultaneously  (105-109  flashes  per  minute,  in  one  instance),  with  regular 
intervals  of  darkness.  This  rare  phenomenon,  to  which  Professor  E.  S. 
Morse  called  attention,  has  attracted  considerable  interest  in  the 
columns  of  Science.  There  seems  to  be  no  doubt  as  to  the  accuracy  of 
the  observations,  but  an  explanation  as  to  how  the  synchronism  is 
effected  and  regulated  is  still  lacking.  The  phenomenon  can  hardly  be 
due  to  chance  when  thousands  of  individuals  are  involved.  The 
fireflies  referred  to,  in  Siam  and  the  Philippines,  belong  to  the  genus 
Calaphotia  (0.  A.  Reinking). 

9.  Respiratory  System 

In  insects,  as  contrasted  with  vertebrates,  the  air  itself  is  conveyed  to 
the  remotest  tissues  by  means  of  an  elaborate  system  of  branching  air- 


ANATOMY    AND    PHYSIOLOGY 


117 


tubes,  or  trachece,  which  receive  air  through  paired  segmentally-arranged 
spiracles.  Each  spiracle  is  commonly  the  mouth  of  a  short  tube  which 
opens  into  a  main  tracheal  trunk  (Fig.  170)  extending  along  the  side  of 
the  body.  From  the  two  main  trunks  branches  are  sent  which  divide 
and  subdivide  and  terminate  in  extremely  dehcate  tubes,  which  pene- 
trate even  between  muscle  fibers;  between  the  ommatidia  of  the  com- 
pound eyes  and  possibly  enter  cells.  In 
most  cases  each  main  longitudinal  trunk 
gives  off  in  each  segment  (Fig.  171)  three 
large  branches:  (i)  an  upper,  or  dorsal, 
branch  which  goes  to  the  dorsal  muscles; 
(2)  a  middle,  or  visceral,  branch,  which 
supplies  the  alimentary  tract  and  the 
reproductive  organs;  (3)  a  lower,  or 
ventral,  branch,  which  pertains  to  the 
ventral  ganglia  and  muscles. 

In  many  swiftly  flying  insects  (dragon 
flies,  beetles,  moths,  flies  and  bees)  there 
occur  tracheal  pockets,  or  air-sacs,  which 
were  formerly  and  erroneously  supposed 
to  diminish  the  weight  of  the  insect,  but 
are  now  regarded  as  simply  air-reser- 
voirs. Sacs  filled  with  air  lessen  the 
specific  gravity  of  an  insect  in  a  fluid 
medium;  but  do  not  increase  the  buoy- 
ancy of  an  insect  in  the  air,  unless  the 
contained  air  is  warmer  than  the  sur- 
rounding air;  and  in  the  case  of  birds, 
it  has  been  found  that  the  air  contained 
in  the  bones,  though  warmer  than  the 

„  ,.  ,  ...  Fig.    170. — Tracheal    system   of   an 

SUrrOUndmg  medmm,  has  no  appreciable    insect,     a,   antenna;    b,    brain;    I,   leg; 

effect  on  flight.  "•  ^^^^^  ^°'"^;    ^'    palpus;  s,  spiracle; 

^      '                    ^  St,  spiracular,  or  stigmatal,   branch;  t, 

T3rpeS    of  Tracheation. Two  types    main  tracheal  trunk;  ?;,  ventral  branch; 

r  ,         1        ,          ,                     T   .•          •  1  1  J-        i>s,  visceral  branch. — After  Kolbe. 

of  tracheal  system  are  distmguished  tor 

convenience:  (i)  the  primary,  open,  or  holopneustic  type  described  above, 
in  which  the  spiracles  are  functional;  (2)  the  secondary,  closed,  or  apneus- 
tic  type,  in  which  the  spiracles  are  either  functionless  or  absent.  This 
type  is  illustrated  in  Collembola  and  such  aquatic  nymphs  and  larvae  as 
breathe  either  directly  through  the  skin  or  else  by  means  of  gills.  The 
two  types  are  connected  by  all  sorts  of  intermediate  stages. 


Il8  ENTOMOLOGY 

Tracheal  Gills. — In  many  aquatic  nymphs  and  larvae  the  spiracles 
are  suppressed  (though  they  become  functional  in  the  imago)  and  res- 


FiG.  171. — Diagrammatic  cross-section  of  the  thorax  of  an  insect,  a,  alimentary  canal; 
d,  dorsal  vessel;  g,  ganglion;  s,  spiracle;  w,  wing;  i,  dorsal  tracheal  branch;  2,  visceral 
branch;  3,  ventral  branch. 

piration  is  effected  by  means  of  gills;  these  are  cuticular  outgrowths 
which  contain  tracheas  and  tracheoles  and  are  commonly  lateral  or 

caudal  in  position.  Lateral  tracheal  gills 
are  highly  developed  in  ephemerid 
nymphs  (Fig.  172),  in  which  a  pair  occurs 
on  some  or  all  of  the  first  seven  segments 
of  the  abdomen;  a  few  genera  have 
cephalic  or  thoracic  gills.  Larvae  of  Tri- 
choptera  have  paired  abdominal  gills 
varying  greatly  in  form  and  position, 
and  Perlidae  often  have  paired  thoracic 
gills.  Caudal  tracheal  gills  are  conspicu- 
ous in  nymphs  of  damsel  flies  (Fig.  173) 
as  three  foliaceous  appendages.  A  few 
coleopterous  larvae  of  aquatic  habit,  as 
Gyrinus  and  Cnemidotus,  possess  tracheal 
Jnof  a'M^  %Ty„S,  'Xi-S  g"'^-  ^  ^o  also  caterpillars  of  the  genus 
variabilis.    Enlarged.  Pam/>owya;  (Fig.  1 74) ,  which  f eed  on  the 

leaves  of  several  kinds  of  water  plants. 

Though  manifold  in  form,  tracheal  gills  are  usually  more  or  less 

foliaceous  or  filamentous,  presenting  always  an  extensive  respiratory 

surface;  their  integument  is  thin  and  the  tracheae  spread  closely  beneath 


ANATOMY   AND   PHYSIOLOGY 


119 


Fig.  173. — Caudal 
gills  of  a  damsel  fly 
nymph,  enlarged. 


it.  These  adaptations  are  often  supplemented  by  waving  movements  of 
the  gills,  as  in  May  fly  nymphs,  and  by  frequent  movements  of  the 
insect  from  one  place  to  another. 

Especially  noteworthy  are  the  rectal  tracheal  gills  of  odonate  nymphs. 
In  these  insects  the  lining  of  the  rectum  forms  numerous  papilla)  or 
lamellae,  which  contain  a  profusion  of  delicate  tra- 
cheal branches;  these  are  bathed  by  water  drawn 
into  the  rectum  and  then  expelled,  at  rather  irregu- 
lar intervals.  A  similar  rectal  respiration  occurs 
also  in  ephemerid  nymphs  and  mosquito  larvae. 

A  few  forms,  chiefly  Perlidae,  are  exceptional  in 
retaining  tracheal  gills  in  the  adult  stage;  in  some 
imagines  they  are  merely  vestiges  of  the  nymphal  gills,  but  in  others, 
such  SiS  Pteronarcys  (Fig.  19),  which  habitually  dips  into  the  water 
and  rests  in  moist  situations,  the  gills  probably  supplement  the  spiracles. 
Further  details  on  the  respiration  of  aquatic  insects 
are  given  in  Chapter  IV. 

Blood-gills. — In  a  few  aquatic  larvae,  Simulium 
and  Chironomus  for  example,  there  are  thin  tubular 
evaginations  of  the  integument  known  as  blood-gills, 
into  which  the  blood  flows.  In  trichopterous  larvae 
(caddis-worms)  the  blood-gills  are  eversible.  Some 
authors  regard  the  ventral  eversible  sacs  of  Scolo- 
pendrella  and  Thysanura,  as  well  as  the  vesicles  of 
the  ventral  tube  of  Collembola,  as  blood-gills. 

Spiracles. — The  paired  external  openings  of  the 
tracheae,  termed  spiracles  or  stigmata,  occur  on  the 
sides  of  the  thorax  and  abdomen;  there  being  not 
more  than  one  pair  to  a  segment,  though  not  all 
segments  bear  them.     As  a  rule,  there  are  two  tho- 
racic and  eight  abdominal  pairs;  these  belonging  to 
Fig.       174. — Cater-  the  mesothorax,  metathorax,  and  first  eight  abdom- 
£l.a/?.  JZTIZ  inal  segments,  respectively.     Adult  insects  do  not 
cheai  gills.  Length,  15  have  morc  than  ten  pairs,  with  the  exception  of 

mm. — After  Hart.  .  ^       e  \ 

Japyx  (see  page  60,  footnote). 

The  spiracles,  variable  in  position,  are  situated  usually  between  two 
segments  of  the  body;  but  often  at  the  anterior  borders  of  the  seg- 
ments to  which  they  belong;  though  they  may  occur  farther  back  on 
the  segments. 

In  most  embryo  insects  there  are  eleven  pairs  of  spiracles — three 


I20  ENTOMOLOGY 

thoracic  and  eight  abdominal;  but  in  adults  the  prothoracic  pair  is 

almost  always  suppressed.     (See  page  60.) 

Though  tracheae  are  absent  in  most  Collembola,  Sminthurides 
aquaticus  has  tracheae  in  the  head,  which  open  through 
a  pair  of  spiracles  on  the  posterior  part  of  the  head, 
there  being  a  spiracle  on  each  side  of  the  neck.  Two 
other  species  of  Collembola,  Sminthurus  fuscus  and 
Actaletes  neptuni,  are  likewise  known  to  have  such  a 
tracheal  system,  limited  to  the  head. 

The  spiracles  are  usually  provided  with  bristles, 
hairs  or  other  processes  to  exclude  dust;  or  the  hairs 
of  the  body  may  serve  the  same  purpose,  as  in  Lepidop- 
tera  and  Diptera;  in  many  beetles  the  spiracles  are  pro- 
tected by  the  elytra;  but  in  other  beetles  and  in  many 
Hemiptera  and  Diptera  the  spiracles  are  unprotected 
externally.  Larvae  that  live  in  water  or  mud  may  have 
Fig.  175.— Larva  spiracles  at  the  end  of  a    long   tube,  which  can  be 

^ciavipes!  ^sh^winl.  thrust  up  into  the  pure  air;  this  is  true  of  the  dipter- 

respiratory  tube.—  Q^g  larvag  of  Eustalis,  BUtacomorpha  (Fig.  175)  and 

Natural  size. — After  i  \      o        i  ^/ 

Hart.  CuUx  (Fig.  232). 

Closure  of  Spiracles. — As  a  rule,  a  spiracle  is  opened 
and  closed  periodically  by  means  of  a  valve,  operated  by  a  special  occ/w^or 
muscle.     In  dipterous  larvae  the  closure  is  effected  by  the  contraction  of 


Fig.  176. — Apparatus  for  closing  the  spiracular  trachea  in  a  beetle,  Lucanus.  A, 
trachea  opened;  B,  closed;  b,  bow;  bd,  band;  c,  external  cuticula;  I,  lever;  m,  muscle;  s, 
spiracle;  t,  trachea. — After  Judeich  and  Nitsche. 


a  circular  muscle,  but  Coleoptera  and  Lepidoptera,  among  other  insects, 
have  a  somewhat  complex  apparatus  for  closing  the  trachea  immediately 
behind  the  spiracle.  Thus,  in  the  stag-beetle,  a  crescentic  bow  (Fig. 
176,  b)  extends  half  around  the  trachea,  and  the  rest  of  the  circumfer- 
ence is  spanned  by  a  lever  (I)  and  a  band  {bd) ;  these  three  chitinous  parts. 


ANATOMY   AND   PHYSIOLOGY 


articulated  together,  form  a  ring  around  the  trachea.  Furthermore,  a 
muscle  (m)  connects  the  lever  and  the  band.  As  the  muscle  shortens, 
the  lever  turning  upon  the  end  of  the  band  as  a  fulcrum,  pulls  the  bow 


Fig.  177. — Structure  of  a 
trachea,  h,  tracheal  hypo- 
dermis;  i,  intima;  I  taenidium. 


Fig.  178. — Tracheolar  end-network  from  silk  gland 
of  Porthelria  dispar.  p,  peritracheal  membrane;  t, 
tracheal   capillary. — After  Wistinghausen. 


toward  the  lever  and  band  until  the  enclosed  trachea  is  pinched  together. 
When  the  muscle  relaxes,  the  trachea  opens  by  its  own  elasticity. 

Structure  of  Tracheae. — The  tracheae  originate  in  the  embryo  as 
simple  in-pocketings  of  the  outer  germ  layer,  or  ectoderm,  and  from 


Pig.  179. — Transverse  sections  of  abdominal  segments  to  illustrate  respiratory  move- 
ments. A,  cockroach  (Blalta);  B,  bee  (Bombus);  s,  sternum;  t,  tergum.  The  dotted  lines 
indicate  positions  of  terga  and  sterna  after  expiration;  the  continuous  lines,  after  inspira- 
tion.— After  Plateau. 

these  the  countless  tracheal  branches  are  derived  by  the  same  process  of 
invagination.  The  lining  membrane  of  a  trachea  is,  then,  continuous 
with  the  external  cuticula,  and  the  cellular  wall  of  a  trachea  is  continu- 
ous with  the  rest  of  the  hypodermis.  This  wall  consists  of  a  layer  of 
polygonal  cells  (Fig,  177)  fitting  closely  together  as  a  pavement  epithe- 
lium. The  chitinous  lining,  or  intima,  is  thickened  at  regular  intervals 
to  form  thread-like  ridges,  which  course  around  the  inner  circumference 


122  ENTOMOLOGY 

in  essentially  a  spiral  manner,  though  the  continuity  of  the  so-called 
spiral  thread  is  frequently  interrupted.  These  elastic  threads,  or 
tcBuidia,  serve  to  keep  the  trachea  open  without  affecting  its  flexibility. 

On  the  outer  surface  of  the  epithelium  is  a  thin  structureless  basement 
membrane. 

Tracheoles. — The  ultimate  divisions  of  the  air-tubes  (Fig.  178)  are 
extremely  delicate  tubes,  or  tracheoles,  which  rarely  end  bhndly,  but 
anastomose  with  one  another,  forming  a  capillary  network  of  confluent 
tubes,  measuring  less  than  o.ooi  mm.  in  diameter,  and  filled,  not  with 
air,  but  with  a  fluid.  Respiration  takes  place  doubtless  by  means  of 
the  tracheoles  rather  than  the  trachese. 

In  a  caterpillar,  these  capillary  tubes  spread  out  over  the  surface  of 
the  cells  of  the  silk-glands,  according  to  Wistinghausen;  and  penetrate 
into  the  gland-cells  themselves,  according  to  Holmgren;  other  authors 
differ  also  as  to  the  relation  of  the  ultimate  branches  of  the  air-tubes  to 
the  cells  which  they  serve. 

The  tracheoles  consist  of  (i)  a  well  developed  peritracheal  membrane, 
which  spreads  out  web-like  between  the  bases  of  the  tubes;  and  (2)  a 
chitinous  intima  without  taenidia;  the  tracheoles  being  connected  with 
the  tracheae  proper  by  means  of  (3)  transition  cells. 

Unlike  tracheae,  the  tracheolar  tubes  do  not  arise  directly  by  in- 
vagination, but  develop  each  within  a  single  cell  of  the  epithelium  of 
a  trachea. 

Respiration. — The  external  signs  of  respiration  are  the  regular  open- 
ing and  closing  movements  of  some  of  the  spiracles  and  the  rhythmic 
contraction  and  expansion  of  the  abdomen.  During  contraction,  the 
dorsal  and  ventral  walls  approach  each  other  (Fig.  179)  and  during 
expansion  they  separate.  The  tergum  moves  more  than  the  sternum 
in  Coleoptera  and  Heteroptera,  and  vice  versa  in  Locustidae,  Odonata, 
Diptera  and  aculeate  Hymenoptera.  The  width  of  the  abdomen  usu- 
ally'changes  but  little  during  respiration,  for  the  tergal  and  sternal 
movements  are  taken  up  by  the  pleural  membranes  which,  as  in  the 
grasshopper,  infold  at  contraction  and  straighten  out  at  expansion. 
Other  respiratory  movements  occur,  but  they  are  of  minor  importance. 

The  rate  of  respiration  increases  or  diminishes  with  the  activity  of 
the  insect  and  with  temperature  and  other  conditions.  In  six  specimens  of 
Melanoplus  diferentialis,  held  between  the  fingers,  the  thoracic  spiracles 
opened  and  closed  respectively  34,  43,  45,  54,  60  and  61  times  per 
minute.  Four  individuals  of  M .  femur -rubrum  under  the  same  circum- 
stances gave  70,  78,  90  and  92. 


ANATOMY   AND   PHYSIOLOGY 


23 


,'k 


At  expansion  inspiration  takes  place,  and  at  contraction  expiration 
occurs.  In  the  grasshopper,  the  thoracic  spiracles  open  almost  simul- 
taneously with  the  expansion  of  the  abdomen.  Contraction  is  effected 
by  special  vertical  expiratory  muscles  (Fig.  180),  but  expansion  is  due 
to  the  elasticity  of  the  abdominal  wall,  as  a  rule;  this  is  the  reverse  of 
what  occurs  in  mammals,  where  expiration  is  passive  and  inspiration 
active.  Inspiratory  muscles  are 
found,  however,  in  Locustidae,  Tri- 
choptera  and  Hymenoptera. 

Though  the  respiratory  move- 
Hients  of  an  insect  may  be  studied 
with  a  hand-lens,  a  more  precise 
method  is  that  of  Plateau — the  chief 
authority  on  insect  physiology — who 
made  use  of  the  stereopticon  to  pro- 
ject an  enlarged  profile  of  the  insect 
upon  a  screen,  on  which  could  be 
marked  the  different  contours  of  the 
abdomen  at  its  phases  of  inspiration 
and  expiration. 

The  way  in  which  the  air  reaches     fig.  i 80.— Diagrammatic  cross-section 
the  finest   tracheal  branches  is  not  of  abdomen  of  a  grasshopper,  rroz-idacn^. 

a,  dorsal  septum,  or  diaphragm;  e*,  expira- 
Clearly  ascertained,  but  it  is  thought  tory  muscle;  /,  fat-body;  g,  gangHon;  K 
.•i-.-r  j-ii-T-  4-u        u       heart;    in,  inspiratory  muscle;  v,  ventral 

that  air  is  forced  into  these  tubes  by  ^.p^^^,  ^eiow  which  is  the  ventral  sinus. 

pressure  from  the  abdominal  muscles,    The  dorsal  and  ventral  septa  rise  and  fall 
.  .  periodically. — After  Graber. 

while  its  escape  through  the  spiracles 

is  being  prevented  by  the  compression  of  the  stigmatal  tracheae. 
The  respiratory  movements  are  entirely  reflex  and  are  independent 
of  the  brain  or  suboesophageal  ganglion,  for  they  continue  after  decapi- 
tation and  even  in  the  detached  abdomen  of  a  grasshopper  or  dragon 
fly.  Each  ventral  ganglion  of  the  body  is  an  independent  respiratory 
center  for  its  particular  segment. 


10.  Reproductive  System 


The  sexes  are  always  separate  in  insects,  hermaphroditism  occurring 
only  as  an  abnormal  condition.  The  sexual  organs,  situated  in  the  ab- 
domen, consist  essentially  of  a  pair  of  ovaries  or  testes  and  a  pair  of  ducts 
(oviducts  or  seminal  ducts,  respectively).  Primitively,  the  ducts  open 
separately,  as  they  still  do  in  Ephemeridae,  but  in  almost  all  other  insects 


124 


ENTOMOLOGY 


the  two  ducts  enter  a  common  evacuating  duct  {vagina  or  ejaculatory 
duct).  The  vagina  commonly  opens  just  behind  the  eighth  abdominal 
sternite,  and  the  ejaculatory  duct  behind  the  ninth. 


Fig.  i8i. — Reproductive  system  of  male 
beetle,  Melolontha.  a,  accessory  gland;  c,  copu- 
latory  organ;  d,  ejaculatory  duct;  s,  seminal 
vesicle;  t,  testis;  2/,vas  deferens. — After  Kolbe, 


Fig.  182.  —  Reproductive  system  of 
male  Lepidoptera.  a,  accessory  gland; 
d,  ejaculatory  duct;  /,  united  testes;  v, 
vas  deferens. — After  Kolbe. 


Homologies. — As   in   other   animals,    the   reproductive  organs  are 
homologous  in  the  two  sexes.     Thus: 


Male 


Female 


Testes  =  Ovaries 
Seminal  ducts  =  Oviducts 
Ejaculatory  duct  =  Vagina 

Seminal  vesicle  =  Seminal  receptacle 
Accessory  glands  =  Accessory  glands 
Penis  and  accessories  =  Ovipositor 

Male  Organs.- — Each  testis,  though  sometimes  a  single  blind  tube,  is 
usually  a  group  of  tubes  or  sacs  (Fig.  181),  testicular  follicles ,  which  open 
into  a  seminal  duct  (vas  deferens) .  In  most  Lepidoptera  the  testes  are 
secondarily  united  into  a  single  mass  (Fig.  182)  as  also  in  Locustidae. 
The  two  seminal  ducts  enter  the  common  ejaculatory  duct,  which  termi- 
nates in  the  intromittent  organ,  or  penis.  Often  each  vas  deferens  is 
dilated  near  its  mouth  into  a  seminal  vesicle,  or  reservoir;  or  there  may  be 
only  a  single  seminal  vesicle,  arising  from  the  common  duct.  One  or 
more  pairs  of  glands  opening  into  the  vasa  deferentia  or  the  ductus 
ejaculatorius  secrete  a  fluid  which  mixes  with  the  spermatozoa  and 
oftentimes  unites  them  into  packets,  known  as  spermatophores. 

All  these  parts  are  subservient  to  the  formation,  preservation  and 
emission  of  the  spermatozoa.     These  minute,  thread-like  bodies  (Fig. 


ANATOMY   AND    PHYSIOLOGY 


183)  arise  in  the  testicular  follicles  from  a  germinal  epithelium,  and 
consist,  as  in  vertebrates,  of  a  head,  middle-piece  and  a  vibratile  tail — 
without  entering  into  the  liner  structure. 

Female  Organs. — Each  ovai^y  (Fig.  184)  consists  of  one  or  more 
tubes  opening  into  an  oviduct.  The  two  oviducts  enter  a  common  duct, 
the  vagina,  which  opens  to  the  exterior,  often  through  an  ovipositor. 
Frequently  the  vagina  is  expanded  as  a  pouch, 
or  bursa  copulatrix,  though  in  Lepidoptera 
the  bursa  and  the  vagina  are  distinct  from 
each  other  and  open  separately  (Fig.  185). 
In  most  insects  a  dorsal  evagination  of  the 
vagina  forms  a  seminal  receptach,  or  sperma- 
theca,  from  which  spermatozoa  emerge  to 
fertilize  the  eggs.  The  accessory  glands, 
either  paired  or  single,  provide  a  secretion  for 
attaching  the  eggs  to  foreign  objects,  cement- 
ing the  eggs  together,  forming  an  egg-capsule, 
etc. 

In  each  ovarian  tube,  or  ovariole,  are  found 
ova  in  successive  stages  of  growth,  the  largest 
and  oldest  ovum  being  nearest  the  oviduct. 
In  the  primitive  type  of  egg- tube,  as  in  Thy- 
sanura  and  Orthoptera  (Fig.  186,  A)  every 
chamber  contains  an  ovum;  in  more  special- 
ized types,  every  other  chamber  contains  a 
nutritive  cell  instead  of  a  germ  cell,  the  nutri- 
tive cells  serving  as  food  for  the  adjacent  ova  {B) ;  or  the  nutritive  cells, 
instead  of  alternating  with  the  ova,  may  be  collected  in  a  special 
chamber,  beyond  the  ovarian  chambers  (C).  An  egg-tube  is  usually 
prolonged  distally  as  a  terminal  filament  or  suspensor,  the  free  end  of 
which  is  attached  near  the  dorsal  vessel. 

Ovaries  and  testes  arise  from  indifferent  cell  or  primitive  germ  cells, 
which  are  at  first  exactly  alike  in  the  two  sexes.  In  the  female,  certain 
of  these  cells  form  ova  and  others  form  a,  follicle  around  each  ovum  (Fig. 
187).  In  the  male,  the  primary  germ  cells  form  cells  termed  spermato- 
gonia; each  of  these  forms  a  spermatocyte,  and  this  gives  rise  to  four 
spermatozoa. 

Hermaphroditism. — The  phenomenon  of  hermaphroditism,  defined 
as  "the  union,  real  or  apparent,  of  the  two  sexes  in  the  same  individual," 
occurs  among  insects  only  as  an  extremely  rare  abnormality  (except  in 


Fig.  183.  —  Spermatozoa. 
A,  grasshopper;  B,  cockroach, 
Blatla;  C,  beetle,  Copris. — Af- 
ter BiJTSCHLi  and  Ballowitz. 


126 


ENTOMOLOGY 


Termitoxinia,  mentioned  beyond).  Speyer  estimated  that  in  Lepidop- 
tera  only  one  individual  in  thirty  thousand  is  hermaphroditic.  Bertkau 
(1889)  Hsted  335  hermaphroditic  arthropods,  of  which  8  were  crusta- 
ceans, 2  spiders,  2  Orthoptera,  8  Diptera,  9  Coleoptera,  51  Hymenoptera 
and  255  Lepidoptera.  The  large  proportion  of  Lepidoptera  is  due  in 
great  measure  to  the  fact  that  they  are  collected  oftener  thaa 'other 
insects  (excepting  possibly  Coleoptera)   and  that  sexual  dimorphism 


Fig.  184. — Reproductive  system  of  queen 
honey  bee.  a,  accessory  sac  of  vagina;  h, 
bulb  of  stinging  apparatus;  c,  colleterial,  or 
cement,  gland;  o,  ovary;  od,  oviduct;  p, 
poison  glands;  pr,  poison  reservoir;  r,  recep- 
taculum  seminis;  re,  rectum;  v,  vagina. — 
After  Leuckart. 


Fig.  185. — Reproductive  system  of 
female  Lepidoptera.  b,  bursa  copulatrix;  /, 
terminal  filament;  g,  cement  glands;  o,  o, 
ovaries;  od,  oviduct;  r,  receptaculum 
seminis;  v,  vagina;  vs,  vestibule,  or  entrance 
to  bursa. — After  Kolbe. 


is  so  prevalent  in  the  order  that  hermaphrodites  are  easily  recognized. 

The  most  common  kind  of  hermaphroditism  is  that  in  which  one 
side  is  male  and  the  other  female,  as  in  Fig.  188.  Bertkau  found  this 
right-and-left  hermaphroditism  in  153  individuals.  In  other  instances 
the  antero-posterior  kind  may  occur,  as  when  the  fore  wings  are  of  one 
sex  and  the  hind  wings  of  the  other;  rarely,  the  characters  of  the  two 
sexes  are  intermingled. 

Hermaphroditic  insects  are  such  rarities  that  very  few  of  them  have 
been  sacrificed  to  the  dissecting  needle  in  order  to  determine  whether  the 
phenomenon  involves  the  primary  organs  as  well  as  the  secondary 
sexual  characters.  Where  dissections  have  been  made  it  has  been 
found  usually  that  hermaphroditism  does  extend  to  the  reproductive 


ANATOMY    AND    PHYSIOLOGY 


127 


organs  themselves.  Thus  a  butterfly  with  male  wings  on  the  right  side 
and  female  wings  on  the  left  would  have  a  testis  on  the  right  side  of  the 
abdomen  and  an  ovary  on  the  left  side. 

True  hermaphroditism,  existing  "only  when  the  essential  organs  of 
reproduction  are  united  in  one  individual," 
and  are  functional,  is  said  to  occur  nor- 
mally in  a  peculiar  wingless  termitophilous 
fly,  Termitoxinia.  Other  instances  of  her- 
maphroditism among  insects  are,  strictly 


Fig.  186. — Types  of  ovarian 
tubes.  A ,  without  nutritive  cells ; 
B,  with  alternating  nutritive  and 
egg-cells;  C,  with  terminal  nutri- 
tive chamber,  c,  terminal  chamber; 
e,  egg-cell;  e/>,  follicle  epithelium; 
/,  terminal  filament;  s,  strands 
connecting  ova  with  nutritive 
chamber;  y,  yolk,  or  nutritive 
cells. — Prom  Lang's  Lehrbuch. 


Fig.  187. — Ovum  of  a  butterfly,  Vanessa,  inits  fol- 
licle, e,  follicle  epithelium;  g,  germinal  vesicle;  n, 
branching  nucleus  of  nutritive  cell;  o,  ovum. — After 

WOODWORTH. 


speaking,  examples  of  gynandromorphism, 
in  which  secondary  sexual  characters  of 
both  sexes  occur  in  the  same  individual. 
A  gynandromorph  often  has  ovaries  and 
testes  at  the  same  time,  but  both  are  not 
functional. 
Parthenogenesis. — Reproduction  without  fertilization  is  a  normal 
phenomenon  in  not  a  few  insects.  This  parthenogenesis  may  easily  be 
observed  in  plant  lice.  In  these  insects  there  are  many  successive 
broods  consisting  of  females  only,  which  bring  forth  living  young;  at 
definite  intervals,  however,  and  usually  in  autumn,  males  appear  also, 
and  fertilized  eggs  are  laid  which  last  over  winter.  This  cycKc  reproduc- 
tion, by  the  way,  is  known  as  heterogeny.  Among  Hymenoptera, 
parthenogenesis  is  prevalent,  usually  alternating  with  sexual  reproduc- 
tion, as  in  many  Cynipidae.     In  some  Cynipidae,  however,  males  are 


128 


ENTOMOLOGY 


Pig.  1 88. — Gynandromorphic  gipsy  moth, 
Porthelria  dispar;  right  side,  male;  left,  female. 
Natural  size. — After  Taschenberg  from  Hert- 
wig's  Lehrbuch. 


unknown;  such  is  the  case  also  in  some  Tenthredinidae.  The  statement 
has  long  been  made  that  the  unfertihzed  eggs  of  worker  ants,  bees  and 
wasps  produce  invariably  males;  it  has  been  found,  however,  that 
the  parthenogenetic  worker  eggs  of  the  ant  Lasius  niger  may  produce 
normal  workers  (Reichenbach, 
Mrs.  A.  B.  Comstock). 

In  the  honey  bee,  unfertil- 
ized eggs  produce  always  males; 
and  it  is  at  present  rather  gen- 
erally believed  that  drones  are 
not  produced  from  fertilized 
eggs. 

Professor  A.  F.  Shull  deter- 
mined experimentally  that  un- 
fertilized eggs  of  the  thysanop- 
teran,  Anthothrips  verhasci  pro- 
duce only  males;  and  concluded 

also  that  fertilized  eggs  produce  only  females.  Parthenogenesis  has 
been  recorded  as  occurring  also  in  a  few  moths,  some  Coccidae  and 
many  Thysanoptera. 

Paedogenesis. — In  Miastor  and  a  few  other  genera  of  Itonididae 
young  are  produced  by  the  larva.  This  extraordinary  form  of  partheno- 
genesis is  termed  pedogenesis,  and  is  limited  apparently  to  the  family 

Itonididae.  The  paedogenetic 
larvae  of  Miastor  (Fig.  189) 
develop  before  the  oviducts 
have  appeared  and  escape  by 
the  rupture  of  the  mother. 
After  several  successive  gener- 
ations of  this  kind  the  result- 
ing larvae  pupate  and  form  normal  male  and  female  flies  . 

An  excellent  account  of  Miastor  has  been  given  by  Dr.  Felt,  who 
has  discovered  this  remarkable  genus  in  New  York  State. 

The  pupa  of  a  species  of  Chironomus  occasionally  deposits  unfer- 
tihzed eggs,  which  develop,  however,  in  the  same  manner  as  the 
fertilized  eggs  of  the  species. 


Fig.  189. — Young  paedogenetic  larvae  of  Miastor 
in  the  body  of  the  mother  larva.  Greatly  enlarged. 
— After  PagenstecheR. 


CHAPTER  III 


DEVELOPMENT 

I.  Embryology 

Ovum. — The  ovum  of  an  insect,  as  of  any  other  animal,  is  a  single 
cell  (Fig.  190),  witha  large  nucleus  (germinal  vesicle),  a  \a,rge  nucleolus, 
nutritive  matter,  or  yolk  {deulo plasm) ,  contained  in  cytoplasm,  and  a 
cell  wall  {vitelline  membrane)  secreted  by  the  ovum. 
The  egg-shell,  or  chorion,  is  secreted  around  the 
ovum  by  surrounding  ovarian  cells. 

Maturation. — As  a  preparation  for  fertilization 
the  germinal  vesicle  divides  twice,  forming  two 
polar  bodies,  and  as  the  first  of  these  bodies  may 
itself  divide,  there  result  four  cells;  three  of  these, 
however — the  polar  bodies — are  minute  and  rudi- 
mentary. 

These  phenomena  of  ovogenesis  are  paralleled 
in  the  development  of  the  spermatozoa,  or  sperma- 
togenesis; for  the  primary  spermatocyte  gives  rise 
to  two  secondary  spermatocytes,  and  these  to  four 
spermatids,  each  of  which  forms  a  spermatozoon. 

By  means  of  this  maturation  process  the  number 
of  chromosomes  in  the  egg-nucleus  is  reduced  to 
half  the  number  normal  for  somatic  cells  (body 
cells  as  distinguished  from  germ  cells).  A  simi- 
lar reduction  occurs  also  during  the  develop- 
ment of  the  spermatozoon,  and  when  sperm-nucleus 
and  egg-nucleus  unite,  the  resulting  nucleus  con- 
tains the  normal  number  of  chromosomes.  The 
meaning  of  these  reduction  phenomena — highly 
important  from  the  standpoint  of  heredity — is  a 
much  debated  subject. 

Fertilization. — As  the  eggs  pass  through  the 
vagina,  they  are  capable  of    being   fertihzed    by 

■  spermatozoa,    previously   stored  in  the  seminal  receptacle.     Through 
the   micropyle  of  the  chorion  one  or  more  spermatozoa  enter  and  a 
9  129 


Pig.  190.  —  Sagittal 
section  of  egg  of  fiy, 
Musca,  in  process  of  fer- 
tilization, c,  chorion;  d, 
dorsal;  m,  micropyle, 
with  gelatinous  exuda- 
tion; p,  male  and  female 
pronuclei,  before  union; 
pb,  polar  bodies;  pr, 
peripheral  protoplasm; 
V,  ventral;  vt,  vitelline 
membrane ;  y,  yolk. — 
After  H  E  N  K I N  G  and 
Blochmann. 


I30 


ENTOMOLOGY 


Fig.  191. — Equatorial  section  of  egg  of  a  beetle, 
Clytra  Iceviuscida.  b,  blastoderm; 5,  germ  band; 
y,  yolk  granule;  yc,  yolk  cell.- — After  Lecaillon. 


sperm  nucleus  unites  with  the  egg-nucleus  to  form  what  is  known  as 
the  segmentation  nucleus.  Through  this  union  of  nuclear  substances 
the    qualities    of   the    two   parents    are   combined    in  the    offspring. 

Needless  to  say,  the  minute 
details  of  the  process  of  fertili- 
zation are  of  the  highest  bio- 
logical importance. 

Blastoderm. — In  an  arthro- 
pod ovum  the  yolk  occupies  a 
central  position  {centrolecithal 
type),  being  enclosed  in  a  thin 
layer  of  protoplasm.  From  the 
segmentation  nucleus  just  men- 
tioned are  derived  many  nuclei, 
some  of  which  migrate  out- 
ward with  their  attendant  pro- 
toplasm to  form  with  the 
original  peripheral  protoplasm 
a  continuous  cellular  layer,  the 
blastoderm  (Fig.  191). 
Germ  Band.— The  blastoderm,  at  first  of  uniform  thickness,  be- 
comes thicker  in  one  region,  by  cell  multiplication,  forming  the  germ 
hand  {primitive  streak,  etc.);  this  appears  in  surface  view  as  an  oval 
or  elongate  area,  denser  than  the  remaining  blastoderm,  with  which 
it  is,  of  course,  continuous. 

Gastmlation. — The  germ  band  next  infolds  along  the  median  line, 

appearing  in  cross- 
section  as  in  Fig.  192 ; 
the  two  lips  of  the 
median  groove  dost  to- 
gether over  the  invagi- 
nated  portion  and 
form  an  outer  layer,  or 
ectoderm  (Fig.  193), 
while  the  invagi- 
nated  portion  spreads 
out  as  an  inner  layer,  which  is  destined  to  form  two  layers,  known 
respectively  as  entoderm  and  mesoderm.  This  formation  of  two  primary 
germ  layers  by  invagination  or  otherwise  is  termed  gastrulation;  it  is 
an  important  stage  in  the  development  of  all  eggs,  and  among  insects 
several  variations  of  the  process  occur. 


Fig.  192. — Transverse   section  of  germ  band  of  Clytra  at 
gastrulation.    g,  germ  band; «,  inner  layer. — After  LecaillON. 


DEVELOPMENT 


131 


Amnion  and  Serosa. — Meanwhile,  the  blastoderm  has  been  folding 
over  the  germ  band  from  either  side,  as  shown  in  Fig.  192,  and  at  length 
the  two  folds  meet  and  unite  to  form  two  membranes  (Fig.  194),  namely, 
an  inner  one,  or  amnion,  and  an  outer  one,  or  serosa. 


^O^^^' 


Fig.  193. — Transverse  section  of  germ 
layers  and  amnion  folds  of  Clytra.  a,  am- 
nion; e,  ectoderm;  i,  inner  layer  (meso- 
entoderm);  s,  serosa. — Original,  based  on 
L^caillon's  figures. 


Fig.  194. — Transverse  section  of  germ 
layers  and  embryonal  membranes  of  Clytra. 
a,  amnion;  ac,  amnion  cavity;  e,  ectoderm; 
i,-  inner  layer  (meso-entoderm) ;  s,  serosa. — 
After  Lecaillon. 


Segmentation  and  Appendages. — On  the  germ  band,  which  repre- 
sents the  ventral  part  of  the  future  insect,  the  body  segments  are  marked 
off  by  transverse  grooves  (Figs.  195,  197) ;  this  segmentation  beginning 


ii^l^ 


Fig.  195. — Germ  band  of  a  beetle,  Lina,  in  three  successive  stages.  A,  unsegmented; 
B,  with  oral  segments  demarkated;  C,  with  three  oral,  three  thoracic  and  two  abdominal 
segments. — After  Graber. 

usually  at  the  anterior  end  of  the  germ  band  and  progressing  backward. 
Furthermore,  an  anterior  infolding  occurs  (Fig.  196),  forming  the  stomo- 
dceum,  from  which  the  mouth,  pharynx,  oesophagus  and  other  parts  of 
the  fore  gut  are  to  arise;  a  similar  but  posterior  invagination,  or  procto- 
dcBum  (Fig.  196),  is  the  beginning,  or  fundament,  of  the  hind  gut. 


,'p 


132  ENTOMOLOGY 

At  the  anterior  end  of  the  germ  band  is  a  pair  of  large  procephalic 
lobes  (Figs.  195,  197),  which  eventually  bear  the  lateral  eyes,  and  im- 
mediately behind  these  are  the 
fundaments  of  the  antennas.  The 
fundaments  of  the  primary  paired 
appendages  are  out-pocketings  of  the 
ectodermal  germ  band,  and  at  first 
antennae,  mouth  parts  and  legs  are 
all  alike,  except  in  their  relative 
positions.  Behind  the  antennae  (in 
Thysanura  and  Collembola  at  least) 
appears  a  pair  of  rudimentary 
appendages  (Fig.  197,  i)  which  are  thought  to  represent  the  second 
antennae  of  Crustacea;  instead  of  developing,  they  disappear  in  the 
embryo  or  else  persist  in  the  adult  as  mere  rudiments.     In  front  of  these 


5  Fig.  196. — Diagrammatic  sagittal  sec- 
tion of  hymenopterous  egg  to  show 
stomodffial  (s)  and  proctodaeal  (p)  in- 
vaginations of  the  germ  band  (g). — 
After  Graber. 


,aJ.l.ia:-/i 


-t2 


-pr 


Fig.  197. — Ventral  aspect  of  germ 
band  of  a  coUembolan,  A  nurida  tnarit- 
ima.  a,  antenna;  a^-a",  abdominal 
appendages;  i,  intercalary  append- 
age; I,  labrum;  U,  left  labial  append- 
age; w,  mandible;  tnx,  maxilla;  p, 
procephalic  lobe;  pr,  proctodaeum; 
"-/',  thoracic  legs. 


P-4~~ 


si  I 


Fig.  198. — Anterior  aspect  of  embryonal  mouth 
parts  of  a  coUembolan,  Anurida  inaritima.  a, 
antenna ;  /,  labrum ;  Ig,  prothoracic  leg ;  It,  left  funda- 
ment of  labium;  In,  lingua;  m,  mandible;  mx,  max- 
illa; p,  maxillary  palpus;  si,    superlingua.- — After 

FOLSOM. 


transitory  intercalary  appendages  is  the  mouth-opening,  above  which 
the  labrum  and  clypeus  are  already  indicated  by  a  single,  median 
evagination.     Behind  the  mouth  the  mandibles,  maxillae  and  labium  are 


DEVELOPMENT 


^33 


represented  by  three  pairs  of  fundaments,  and  in  Thysanura  and 
Collembola  a  fourth  pair  is  present  to  form  the  superlinguae  (Fig.  198,  si), 
already  referred  to.  Next  in  order  are  the  three  pairs  of  thoracic  legs 
(Fig.  197)  and  then,  in  many  cases,  paired  abdominal  appendages  (Figs. 
197,  199),  indicating  an  ancestral  myriopod-like  condition;  some  of  these 
abdominal  Hmbs  disappear  in  the  embryo  but  others  develop  into  abdom- 
inal prolegs  (Lepidoptera  and  Tenthre-  ^  ^ 
dinidae),  external  genital  organs  (Orthop- 
tera,  Hymenoptera,  etc.)  or  other  structures. 
The  study  of  these  embryonic  fundaments 
sheds  much  light  upon  the  morphology  of 
the  appendages  and  the  subject  of  segmen- 
tation. 

Two  Types  of  Germ  Bands. — The  germ 
band  described  above  belongs  to  the  simple 
overgrown  type,  exemplified  in  Clytra,  in 
which  the  germ  band  retains  its  original 
position  and  the  amnion  and  serosa  arise  by 
a  process  of  overgrowth  (Figs.  193,  194),  as 
distinguished  from  the  invaginated  type, 
illustrated  in  Odonata,  in  which  the  germ 
band  invaginates  into  the  egg,  as  in  Fig. 
200,  until  the  ventral  surface  of  the  embryo 
becomes  turned  around  and  faces  the  dorsal 
side  of  the  egg.  In  this  event,  a  subse- 
quent process  of  revolution  occurs,  by 
means  of  which  the  ventral  surface  of  the 
embryo  resumes  its  original  position  (Fig. 
201). 

Dorsal  Closure. — As  was  said,  the  germ 
band  forms  the  ventral  part  of  the  insect. 
To  complete  the  general  form  of  the  body 
the  margins  of  the  germ  band  extend  out- 
ward   and   upward   (Fig.    202)    until   they 

finally  close  over  to  form  the  dorsal  wall  of  the  insect.  Besides  this 
simple  method,  however,  there  are  several  other  ways  in  which  the 
dorsal  closure  may  be  effected. 

Nervous  System. — Soon  after  gastrulation,  the  ventral  nervous 
system  arises  as  a  pair  of  parallel  cords  from  cells  (Fig.  203,  n)  which 
have  been  derived  by  direct  proliferation  from  those  of  the  germ  band, 


Fig.  199. — Embryo  of  CEcan- 
Ihus,  ventral  aspect,  a,  antenna; 
a^a^,  abdominal  appendages;  e, 
end  of  abdomen;  /,  labrum;  li, 
left  fundament  of  labium;  Ip, 
labial  palpus;  l^l^,  thoracic  legs; 
m,  mandible;  mp,  maxillary- 
palpus;  mx,  maxilla;  p,  pro- 
cephalic  lobe;  pr,  proctodseum. 
— After  Ayers. 


[34 


ENTOMOLOGY 


and  are  therefore  ectodermal  in  origin.  This  primitive  double  nerve 
cord  becomes  constricted  at  intervals  into  segments,  or  neuromeres, 
which  correspond  to  the  segments  of  the  germ  band.     Each  neuromere 


Fig.   200.— Diagrammatic  sagittal  sections  to  illustrate  invagination  of  germ  band  in 
Calopteryx.     a,  anterior  pole;  ac,  amnion  cavity;  am,  amnion;  b,  blastoderm;  d,  dorsal; 
g,  germ  band;  h,  head  end  of  germ  band;  p,  posterior  pole; 
After  Brandt. 


serosa;  v,  ventral;  y,  yolk.- 


PiG.  201. — Diagrammatic  sagittal  sections  to  illustrate  revolution  of  Calopteryx 
embryo,  a,  antenna;  am,  amnion;  I,  labium;  l^P,  thoracic  legs;  w,  mandible;  mx.  maxilla; 
5,  serosa. — After  Brandt. 


consists  of  a  pair  of  primitive  ganglia,  and  these  are  connected  together 
by  paired  nerve  cords,  which  later  may  or  may  not  unite  into  single 
cords;  moreover,  some  of  the  ganglia  finally  unite  to  form  compound 
ganglia,  such  as  the  brain  and  the  sub  oesophageal  ganglion.     In  front  of 


DEVELOPMENT 


135 


the  oesophagus  (Fig.  57)  are  three  neuromeres:  (i)  protocerehrum,  which 
is  to  bear  the  compound  eyes;  (2)  deulocerehrum,  or  antennal  neuromere; 
(3)  tritocerehrum,  which  belongs  to  the  segment  which  bears  the  rudi- 
mentary intercalary  appendages  spoken  of  above.  Behind  the  oesopha- 
gus are,  at  most,  four  neuromeres,  namely  and  in  order,  mandibular, 
superUtigual  (found  only  in  Collembola  as  yet),  maxillary  and  labial. 


Fig.  202. — Diagrammatic  transverse  sections  to  illustrate  formation  of  dorsal  wall  in 
the  beetle,  Leptinotarsa.  a,  amnion  (breaking  up  in  C);  g,  germ  band;  5,  serosa.— After 
Wheeler,  from  the  Journal  of  Morphology. 

Then  follow  the  three  thoracic  ganglia  and  ten  or  eleven  abdominal 
ganglia.  The  first  three  neuromeres  always  unite  to  form  the  brain, 
and  the  next  four  (always  three;  but  four  in  Collembola  and  perhaps 
other  insects) ,  to  form  the  suboesophageal  gangHon.  Compound 
ganglia  are  frequently  formed  also  in  the  thorax  and  abdomen  by  the 
union  of  primitive  ganglia. 

Tracheae. — The  tracheae  begin  as  paired  invaginations  of  the  ecto- 
derm (Fig.  204,  /) ;  these  simple  pockets  elongate  and  unite  to  form  the 
main   lateral    trunks,    from 
which    arise   the    countless 
branches    of    the    tracheal 
system. 

Mesoderm. — From  the 
inner  layer  which  was  derived 
from  the  germ  band  by  gas- 
trulation  (Figs.  192-194)  are 
formed  the  important  germ 

layers  known  as  mesoderm  and  entoderm.  Most  of  the  layer  becomes 
mesoderm,  and  this  splits  on  either  side  into  chambers,  or  ccelom 
sacs  (Fig.  203,  c),  a  pair  to  each  segment.  In  Orthoptera  these 
coelom  sacs  are  large  and  extend  into  the  embryonic  appendages,  but  in 
Coleoptera,  Lepidoptera  and  Hymenoptera  they  are  small.  These  sacs 
may  share  in  the  formation  of  the  definite  body-cavity,  though  the  last 
arises  independently,  from  spaces  that  form  between  the  yolk  and  the 


Pig.  203. — Transverse,  section  of  germ  layers 
of  elytra,  c,  coelom  sac;  n,  neuroblasts  (primi- 
tive nervous  cells). — After  Lecaillon. 


i^b 


ENTOMOLOGY 


mesodermal  tissues.  From  the  coelom  sacs  develop  the  muscles,  fat- 
body,  dorsal  vessel,  blood  corpuscles,  ovaries  and  testes;  the  external 
sexual  organs,  however,  as  well  as  the  vagina  and  ejaculatory  duct,  are 
ectodermal  in  origin. 

Entoderm. — At  its  anterior  and  posterior  ends,  the  inner  layer  just 
referred  to  gives  rise  to  a  mass  of  cells  which  are  destined  to  form  the 
mesenteron,  from  which  the  mid  intestine  develops.  One  mass  is  ad- 
jacent to  the  Wind  end  of  the  stomodaeal  invagination  and  the  other  to 
that  of  the  proctodaeal  in-folding.  The  two  masses  become  U-shaped 
(Fig.  205),  and  the  lateral  arms  of  the  two  elongate  and  join  so  that  the 
entodermal  masses  become  connected  by  two  lateral  strands  of  cells; 


Fig.  204. — Transverse  section  ot  abdomen  of  Clylra  embryo  at  Fig.    205. — Dia- 

an  advanced  stage  of  development,     a,  appendage;  e,  epithelium  of  gram    of    formation 

mid  intestine;  g,  ganglion;  m,  Malpighian  tube;  mi,  muscular  layer  of  entoderm  in  Lep- 

of  mid  intestine;  W5,  muscle  elements;   my,  mesenchyme  (source  of  linotarsa.     <?,  e,  ento- 

fat-body);  s,  sexual  organ;  t,  tracheal  invagination. — After  Lecail-  dermal    masses;    m, 

LON.  mesoderm. — A  f  t  e  r 

Wheeler. 


by  overgrowth  and  undergrowth  from  these  lateral  strands  a  tube  is 
formed  which  is  destined  to  become  the  stomach,  and  by  the  disappear- 
ance of  the  partitions  that  separate  the  mesenteron  from  the  stomodaeum 
at  one  end  and  from  the  proctodaeum  at  the  other  end,  the  continuity  of 
the  alimentary  canal  is  established.  '  The  fore  and  the  hind  gut,  then, 
are  ectodermal  in  origin,  and  the  mid  gut  entodermal. 

Polyembryony.— In  certain  Hymenoptera  a  single  egg  may  give 
rise  to  many  individuals.  Thus  in  some  Chalcididae  and  Proctotrypidae, 
according  to  Marchal,  the  fertilized  ovum  segments  into  many  (12-100) 
embryos,  which  develop  into  as  many  adults,  all  the  individuals  from  the 
same  ovum  being  of  the  same  sex. 


DEVELOPMENT 


137 


2.  External  Metamorphosis 

Metamorphosis. — One  of  the  most  striking  phenomena  of  insect 
life  is  expressed  by  the  term  metamorphosis,  which  means  conspicuous 
change  of  form  after  birth.  The  egg  of  a  butterfly  produces  a  larva; 
this  eats  and  grows  and  at  length  becomes  a  pupa;  which,  in  turn,  de- 
velops into  an  imago.  These  stages  are  so  different  (Fig.  28)  that  with- 
out experience  one  could  not  know  that  they  pertained  to  the  same 
individual. 

Holometabola. — The  more  specialized  insects,  namely,  Coleoptera 
(Fig.  206),  Strepsiptera,  Neuroptera,  Mecoptera,    Trichoptera,  Lepi- 


FiG.   206. — Cyllene  carya.     A,  larva;  B,  pupa;  C,  imago.       X  3. 


doptera,  Diptera  (Figs.  207,  31),  Siphonaptera  (Fig.  32)  and  Hymenop- 
tera  (Fig.  287),  undergo  this  indirect,  or  complete,^  metamorphosis, 
involving  profound  changes  of  form  and  distinguished  by  the  internal 
development  of  the  wings  and  by  a  pupal  stage  that  is  usually  inactive, 
though  active  in  mosquitoes  and  some  midges,  and  in  certain  Neuroptera 
just  before  the  transformation.  These  insects  are  grouped  together  as 
Holometabola. 

Larvae  receive  such  popular  names  as  "caterpillar"  (Lepidoptera) , 
''grub"  (Coleoptera),  and  "maggot"  (Diptera),  while  the  pupa  of  a 
moth  or  butterfly  (especially  the  latter)  is  called  a  "chrysahs." 


'These  terms,  though  somewhat  misleading  in  implication,  are  currently  used. 


138 


ENTOMOLOGY 


Heterometabola. — In  a  grasshopper,  as  contrasted  with  a  butterfly, 
the  imago,  or  adult,  is  essentially  like  the  young  at  birth,  except  in  hav- 
ing wings  and  mature  reproductive  organs,  and  the  insect  is  active 
throughout  Hfe,  the  wings  developing  externally;  hence  the  meta- 
morphosis is  termed  direct,  or  incomplete.     This  type  of  transformation, 

without  a  true  pupal  period,  is 
characteristic  of  the  more  gener- 
alized of  the  metamorphic  insects, 
namely,  Orthoptera,  Dermaptera, 
Platyptera,  Plecoptera  (Fig.  19), 
Ephemerida  (Fig.  20),  Odonata 
(Fig.  2i),Thysanoptera  and  Hemi- 
ptera  (Fig.  208).  These  orders 
constitute  the  group  Heterome- 
tabola. Within  the  limits  of  the 
group,  however,  various  degrees  of 
metamorphosis  occur;  thus  Plec- 
optera, Ephemerida  and  Odonata 
undergo  considerable  change  of 
form;  a  resting,  or  quiescent,  period  may  precede  the  imaginal  stage, 
as  in  Cicada  (Fig.  209).     In  fact,  the  various  kinds  of  metamorphosis 


Fig 


207. — Phormia    regina. 
puparium;  C,  imago. 


Fig.  208. — Six  successive  instars  of  the  squash  bug,  Anasa  trislls.      x  2. 


grade  into  one  another  in  such  a  way  as  to  make  their  classification  to 
some  extent  arbitrary  and  inadequate. 

As  there  is  no  distinction  between  larva  and  pupa  in  most  hetero- 


DEVELOPMENT 


139 


metabolous  insects,  it  is  customary  to  use  the  term  nymph  during  the 
interval  between  egg  and  imago. 

As  a  rare  abnormality,  a  holometabolous  larva  may  possess  two 
pairs  of  true  external  wing-pads.     This  condition  has  been  reported  in 


Fig.  209. — Cicada  libicen.     A,  imago  emerging  from  nymphal  skin;  B,  the  cast  skin;  C, 
imago.     Natural  size. 

several  specimens  of  the  meal  worm,  Tenebrio  molitor  (by  Heymons),  six 
larvae  of  the  museum  beetle,  Anthrenus  verhasci  (A.  Busck)  and  one 
pyrochroid  larva,  Dendroides  canadensis  (P.  B.  Powell).     In  these  larvae 


Fig.  210. — Eggs  of  various  insects.  A,  butterfly,  Polygonia  interrogalionis;  B,  house 
fly,  Musca  domeslica;  C,  chalcid,  Bruchophagus  funebris;  D,  butterfly,  Papilio  Iroilus;  E, 
midge,  Dasyneura  trifolii;  F,  hemipteron,  Triphleps  insidiosus;  G,  hemipteron,  Podisus 
maculiventris;  H,  fly,  Drosophila  ampelophila.     Greatly  magnified. 


— all  coleopterous — it  is  comparatively  an  easy  step  from  the  internal 
wing-rudiment  to  an  external  wing-pad,  as  Dr.  W.  A.  Riley  has  pointed 
out.  He  regards  the  phenomenon  not  as  an  instance  of  atavism — a 
harking-back  to  a  period  when  the  larva  bore  wings — but  as  an  example 


I40 


ENTOMOLOGY 


Fig.  211. — Three  eggs  of  the  cabbage  butter- 
fly, Pieris  rapa.  Greatly  magnified,  but  all 
drawn  to  same  scale. 


of  a  kind  of  premature  development  (known  as  prothetaly)  in  which 
characters  normally  present  in  the  pupal  state  are  present  abnormally  in 
the  larva.  The  latter  interpretation  is  supported  by  the  fact  that  in 
Mr.  Powell's  specimen,  in  addition  to  the  larval  ocelli,  the  compound 

eyes  of  the  adult  are  partially 
developed,  and  there  are  more 
antennal  segments  than  in  the 
normal  larva. 

Ametabola. — The  most  gen- 
eralized insects,  Thysanura  and 
Collembola,  develop  to  sexual 
maturity  without  a  metamor- 
phosis; the  form  at  hatching  is 
retained  essentially  throughout 
life,  there  are  no  traces  of  wings 
even  in  the  embryo,  and  there  is  no  change  of  habit.  These  two 
orders  form  the  group  Ametabola.  All  other  insects  have  a  metamor- 
phosis in  the  broad  sense  of  the  term,  and  are  therefore  spoken  of  as 
Metahola.  In  this  we  follow  Packard,  rather  than  Brauer,  who  uses  a 
somewhat  different  set  of  terms  to  express  the 
same  ideas. 

Stadium  and  Instar. — During  the  growth 
of  every  insect,  the  skin  is  shed  periodically, 
and  with  each  molt,  or  ecdysis,  the  appearance 
of  the  insect  changes  more  or  less.  The  inter- 
vals between  the  molts  are  termed  stages,  or 
stadia.  '  To  designate  the  insect  at  any  particu- 
lar stage,  the  term  instar  was  proposed  and  is 
much  used;  thus  the  insect  at  hatching  is  the 
first  instar,  after  the  first  molt  the  second  instar, 
and  so  on. 

Eggs. — The  eggs  of  insects  are  exceedingly 
diverse  in  form.  Commonly  they  are  more  or 
less  spherical,  oval,  or  elongate,  but  there  are 
innumerable  special  forms,  some  of  which  are 
quite  fantastic.  Something  of  the  variety  of 
form  is  shown  in  Fig.  210.     As  regards  size, 

most  insect  eggs  can  be  distinguished  by  the  naked  eye;  many  of 
them  tax  the  vision,  however,  for  example,  the  elliptical  eggs  of 
Dasyneura  leguminicola,  which  are  but  .300  mm.  in  length  and  .075 


Fig.  212. — Chrysopa,  laymg 
eggs.      Slightly  enlarged. 


DEVELOPMExM  I4I 

mm.  in  width;  the  oval  eggs  of  the  cecropia  moth,  on  the  other  hand, 
are  as  long  as  3  mm. 

The  egg-shell,  or  chorion,  secreted  around  the  ovum  by  cells  of  the 
ovarian  follicle,  may  be  smooth  but  is  usually  sculptured,  frequently 
with  ridges  which,  as  in  lepidopterous  eggs,  may  serve  to  strengthen  the 
shell.  The  ornamentation  of  the  egg-shell  is  often  exquisitely  beautiful, 
though  the  particular  patterns  displayed  are  probably  of  no  use,  being 
mcidentally  produced  as  impressions  from  the  cells  which  secrete  the 
chorion.  Variations  of  form,  size  and  pattern  are  frequent  in  eggs 
of  the  same  species,  as  appears  in  Fig.  211. 

Always  the  chorion  is  penetrated  by  one  or  more  openings,  constitut- 
ing the  micropyle,  for  the  entrance  of  spermatozoa. 

As  a  rule,  the  eggs  when  laid  are  accompanied  by  a  fluid  of  some  sort, 
which  is  secreted  usually  by  a  cement  gland  or  glands,  opening  into  the 
vagina.  This  fluid  commonly  serves  to  fasten  the  eggs  to  appropriate 
objects,  such  as  food  plants,  the  skin  of  other  insects,  the  hairs  of 
mammals,  etc.;  it  may  form  a  pedicel,  or  stalk,  for  the  egg,  as  in 
Chrysopa  (Fig.  2.12);  may  surround  the  eggs  as  a  gelatinous  envelope, 
as  in  caddis  flies,  dragon  flies,  etc. ;  or  may  form  a  capsule  enclosing  the 
eggs,  as  in  the  cockroach. 

The  number  of  eggs  laid  by  one  female  differs  greatly  in  different 
species  and  varies  considerably  in  different  individuals  of  the  same 
species.  Some  of  the  fossorial  wasps  and  bees  lay  only  a  dozen  or  so  and 
some  grasshoppers  two  or  three  dozen,  while  a  queen  honey  bee  may  lay 
a  million.  Two  females  of  the  beetle  Prionus  laticollis  had,  respectively, 
332  and  597  eggs  in  the  abdomen  (Mann).  A.  A.  Girault  gives  the  fol- 
lowing numbers  of  eggs  per  female,  from  an  examination  of  twenty  egg- 
masses  of  each  species: 

M.^xiMUM  Minimum  Average 

Thyridopteryx  ephememformis  {hdigwoxm) 1649  465  941 

Malacosoma  americana  (tent  caterpillar) 466  313  375-5 

Chionas pis  furf lira  (scurfy  scale) 84  33               66.5 

Hatching. — Many  larvae,  caterpillars  for  example,  simply  eat  their 
way  out  of  the  egg-shell.  Some  maggots  rupture  the  shell  by  contor- 
tions'of  the  body.  Some  larvae  have  special  organs  for  opening  the 
shell;  thus  the  grub  of  the  Colorado  potato  beetle  has  three  pairs  of 
hatching  spines  on  its  body  (Wheeler)  and  the  larval  flea  has  on  its  head 
a  temporary  knife-like  egg-opener  (Packard).  The  process  of  hatching 
varies  greatly  according  to  the  species,  but  has  received  very  little 
attention. 


142 


ENTOMOLOGY 


Larva. — Although  larvae,  generally  speaking,  differ  from  one  another 
much  less  than  their  imagines  do,  they  are  easily  referable  to  their  orders 
and  usually  present  specific  differences.  Larvae  that  display  individual 
adaptive  characters  of  a  positive  kind  (Lepidoptera,  for  example)  are 
easy  to  place,  but  larvae  with  negative  adaptive  characters  (many  Dip- 
tera  and  Hymenoptera)  are  often  hard  to  identify. 

Thysanuriform  Larvae. — Two  types  of  larvae  have  been  recognized 
by  Brauer,  Packard  and  other  authorities:  thysanuriform  and  eruciform; 
respectively  generahzed  and  specialized  in  their  organization.  The 
former  term  is  applied  to  many  larvae  and  nymphs  (Fig.  213,  C)  on 


Fig.  213. — Types  of  larvae.  A,  B,  Thysanura;  C,  thysanuriform  nymph;  E-I,  cruci- 
form larvae.  A,  Campodea;  B,  Lepisma;  C,  perlid  nymph  (Plecoptera) ;  D,  Libellula  (Odo- 
nata);  E,  Tenlhredopsis  (Hymenoptera);  F,  Lachnosterna  (Coleoptera);  G,  Melanotus 
(Coleoptera);  H,  Bombiis  (Hymenoptera);  /,  Hypoderma  (Diptera). 


account  of  their  resemblance  to  Thysanura,  of  which  Campodea  and 
Lepisma  are  types.  The  resemblance  lies  chiefly  in  the  flattened  form, 
long  body,  hard  plates,  long  legs  and  antennae,  caudal  cerci,  well- 
developed  mandibulate  mouth  parts,  and  active  habits,  with  the  accom- 
panying sensory  specializations.  These  characteristics  are  permanent 
in  Thysanura,  but  only  temporary  in  metamorphic  insects,  and  their 
occurrence  in  the  latter  forms  may  properly  be  taken  to  indicate  that 
these  insects  have  been  derived  from  ancestors  which  were  much  like 
Thysanura. 

Thysanuriform  characters  are  most  pronounced  in  nymphs  of  Blat- 
tidae,  Forficulidae,  Perlidae  and  Ephemeridae,  but  occur  also  in  the  larvae 
of  some  Neuroptera  (Mantispa)  and  Coleoptera  (Carabidae  and  Meloi- 
dae).  These  primitive  characters  are  gradually  overpowered,  in  the 
course  of  larval  evolution,  by  secondary,  or  adaptive  features. 


DEVELOPMENT 


f43 


Eruciform  Larvae. — The  prevalent  type  of  larva  among  holometab- 
olous  ipsects  is  the  eruciform  (Fig.  213,  E-I),  illustrated  by  a  caterpillar 
or  a  maggot.  Here  the  body  is  cylindrical  and  often  fleshy;  the  integ- 
ument weak;  the  legs,  antennae,  cerci,  and  mouth  parts  reduced,  often 
to  disappearance;  the  habits  sedentary  and  the  sense  organs  corre- 
spondingly reduced.  These  characteristics  are  interpreted  as  being 
results  of  partial  or  entire  disuse,  the  amount  of  reduction  being  pro- 
portional to  the  degree  of  inactivity.  Extreme  reduction  is  seen  in  the 
maggots  of  parasitic  and  such  other  Diptera  as,  securing  their  food  with 
almost  no  exertion,  are  simple  in  form,  thin-skinned,  legless,  with  only 
a  mere  vestige  of  a  head  and  with  sensory  powers  of  but  the  simplest 
kind. 

Transitional  Forms. — The  eruciform  is  clearly  derived  from  the 


Fig.  214. — Mantispa.  A,  larva  at  hatching — thysanuriform;  B,  same  larva  just  before 
first  molt — now  becoming  eruciform.  C,  imago,  the  wings  omitted;  D,  winged  imago, 
slightly  enlarged. — A  and  B  after  Brauer;  C  and  D  after  Emerton,  from  Packard's  Text- 
Book  of  Entomology,  by  permission  of  the  Macmillan  Co. 


thysanuriform  type,  as  Brauer  and  Packard  have  shown,  the  continuity 
between  the  two  types  being  established  by  means  of  a  complete  series 
of  intermediate  stages.  The  beginning  of  the  eruciform  type  is  found 
in  Neuroptera,  where  the  campodeoid  sialid  larva  assumes  a  quiescent 
pupal  condition.  The  key  to  the  origin  of  the  complete  metamorpho- 
sis, involving  the  eruciform  condition,  Packard  finds  in  the  neuropterous 
genus  Mantispa  (Fig.  214),  the  first  larva  of  which  is  truly  campodei- 
form  and  active.  Beginning  a  sedentary  life,  however,  in  the  egg-sac  of 
a  spider,  it  loses  the  use  of  its  legs  and  the  antennae  become  partly 
aborted,  before  the  first  molt.  In  Packard's  words,  "Owing  to  this 
change  of  habits  and  surroundings  from  those  of  its  active  ancestors,  it 


144  ENTOMOLOGY 

changes  its  form,  and  the  fully  grown  larva  becomes  cylindrical,  with 
small  slender  legs,  and,  owing  to  the  partial  disuse  of  its  jaws,  acquires 
a  small,  round  head."  Meloidae  (Fig.  220)  afford  other  excellent 
examples  of  the  transition  from  the  thysanuriform  to  the  cruciform 
condition  during  the  life  of  the  individual. 

Thysanuriform  characters  become  gradually  suppressed  in  favor  of 
the  cruciform,  until,  in  most  of  the  highly  developed  orders  (Mecoptera, 
Trichoptera,  Lepidoptera,  Diptera,  Siphonaptera  and  Hymenoptera), 
they  cease  to  appear,  except  for  a  few  embryonic  traces— an  illustration 
of  the  principle  of  ''acceleration  in  development." 

Growth. — The  larval  period  is  pre-eminently  one  of  growth.  In 
Heterometabola,  growth  is  continuous  during  the  nymphal  stage,  but 
in  Holometabola  this  important  function  becomes  relegated  to  the  larval 
stage,  and  pupal  development  takes  place  at  the  expense  of  a  reserve 
supply  of  food  accumulated  by  the  larva. 

The  rapidity  of  larval  growth  is  remarkable.  Trouvelot  found  that 
the  caterpillar  of  Telea  polyphemus  attains  in  56  days  4,140  times  its 
original  weight  (|^o  grain),  and  has  eaten  an  amount  of  food  86,000 
times  its  primitive  weight.  Other  larvae  exceed  even  these  figures;  thus 
the  maggot  of  a  common  flesh  fly  attains  200  times  its  original  weight 
in  24  hours. 

Ecdysis. — The  exoskeleton,  unfitted  for  accommodating  itself  to  the 
growth  of  the  insect,  is  periodically  shed,  and  along  with  it  go  not  only 
such  integumentary  structures  as  hairs  and  scales,  but  also  the  chitinous 
lining,  or  intima,  of  the  stombdaeum,  proctodaeum,  tracheae,  integumen- 
tary glands,  etc.  The  process  of  molting,  or  ecdysis,  in  caterpillars  is 
briefly  as  follows.  The  old  skin  becomes  detached  from  the  body  by  an 
intervening  fluid  of  hypodermal  origin;  the  skin  dries,  shrinks,  is  pushed 
backward  by  the  contractions  of  the  larva,  and  at  length  splits  near  the 
head,  frequently  under  the  neck ;  through  this  split  appear  the  new  head 
and  thorax,  and  the  old  skin  is  worked  back  toward  the  tail  until  the 
larva  is  freed  of  its  exuvice.  The  details  of  the  process  are,  however,  by 
no  means  simple.  Ecdysis  is  probably  something  besides  a  provision 
for  growth,  for  Collembola  continue  to  molt  long  after  growth  has 
ceased,  and  the  winged  May  fly  sheds  its  skin  once  after  emergence. 
The  meaning  of  this  is  not  known,  though  ecdysis  has  an  excretory 
importance  in  the  case  of  Collembola,  which  are  exceptional  among 
insects  in  having  no  Malpighian  tubes. 

Number  of  Molts. — The  frequency  of  molting  differs  greatly  in 
different  orders  of  insects.     Locustidae  (formerly  " Acridiidae ")  have 


DEVELOPMENT  1 45 

five  molts;  many  Heteroptera,  as  the  chinch  bug  and  squash  bug,  have 
five  (with  six  instars) ;  the  periodical  cicada,  six  (Marlatt) ;  the  larva  of 
the  Colorado  potato  beetle,  three;  Lepidoptera  usually  four  or  five,  but 
often  more,  as  in  Isia  Isabella,  which  molts  as  many  as  ten  times  (Dyar) ; 
the  house  fly,  Musca  domestica,  two  molts  (three  larval  instars) .  Pack- 
ard suggests  that  cold  and  lack  of  food  during  hibernation  in  arctians 
(as  I.  Isabella)  and  partial  starvation  in  the  case  of  some  beetles,  cause 
a  great  number  of  molts  by  preventing  growth,  the  hypodermis  cells 
meanwhile  retaining  their  activity. 

The  appearance  of  the  insect  often  changes  greatly  with  each  molt, 
particularly  in  caterpillars,  in  which  the  changes  of  coloration  and 
armature  may  have  some  phylogenetic  significance,  as  Weismann  has 
attempted  to  show  in  the  case  of  sphingid  larvae. 

Adaptations  of  Larvae. — Larvae  exhibit,  innumerable  conformities 
of  structure  to  environment.  The  greatest  variety  of  adaptive  struc- 
tures occurs  in  the  most  active  larvae,  such  as  predaceous  forms,  ter- 
restrial or  aquatic.  These  have  well-developed  sense  organs,  excellent 
powers  of  locomotion,  special  protective  and  aggressive  devices,  etc. 
In  insects  as  a  whole,  the  environment  of  the  larva  or  nymph  and  that 
of  the  adult  may  be  very  different,  as  in  the  butterfly  or  the  dragon  fly, 
and  the  larvae  are  modified  in  a  thousand  ways  for  their  own  immediate 
advantage,  without  any  direct  reference  to  the  needs  of  the  imago. 

The  chief  purpose,  so  to  speak,  of  the  larva  is  to  feed  and  grow,  and 
the  largest  modifications  of  the  larva  depend  upon  nutrition.  Take  as 
one  extreme,  the  legless,  headless,  fleshy  and  sluggish  maggot,  embedded 
in  an  abundance  of  food,  and  as  the  other  extreme  the  active  and 
''wide-awake"  larva  of  a  carabid  beetle,  dependent  for  food  upon  its 
own  powers  of  sensation,  locomotion,  prehension,  etc.,  and  obHged 
meanwhile  to  protect  or  defend  itself.  Between  these  extremes  come 
such  forms  as  caterpillars,  active  to  a  moderate  degree.  The  great 
majority  of  larval  characters,  indeed,  are  correlated  with  food  habits, 
directly  or  indirectly;  directly  in  the  case  of  the  mouth  parts,  sensory 
and  locomotor  organs,  and  special  structures  for  obtaining  special  food; 
indirectly,  as  in  respiratory  adaptations  and  protective  structures, 
these  latter  being  numerous  and  varied. 

Larvae  that  live  in  concealment,  as  those  that  burrow  in  the  ground 
or  in  plants,  have  few  if  any  special  protective  structures;  active  larvae, 
as  those  of  Carabidae,  have  an  armor-like  integument,  but  owe  their 
protection  from  enemies  chiefly  to  their  powers  of  locomotion  and  their 
aversion  to  Hght  (negative  phototro  pism) ;  various  aquatic  nymphs  {Z  ait  ha, 


146  ENTOMOLOGY 

Odonata)  are  often  coated  with  mud  and  therefore  difficult  to  distin- 
guish so  long  as  they  do  not  move;  caddis  worms  are  concealed  in  their 
cases,  and  caterpillars  are  often  sheltered  in  a  leafy  nest.  There  is  no 
reason  to  suppose  that  insects  conceal  themselves  consciously,  however, 
and  one  is  not  warranted  in  speaking  of  an  instinct  for  concealment  in  the 
case  of  insects — since  everything  goes  to  show  that  the  propensity  to 
hide,  though  advantageous  indeed,  is  simply  a  reflex,  inevitable,  nega- 
tive reaction  to  light  (negative  phototropism)  or  a  positive  reaction  to 
contact  {positive  thigmotropism). 

Exposed,  sedentary  larvae,  as  those  of  many  Lepidoptera  and  Cole- 
optera,  often  exhibit  highly  developed  protective  adaptations.  Cater- 
pillars may  be  colored  to  match  their  surroundings  and  may  resemble 
twigs,  bird-dung,  etc.;  or  larvae  may  possess  a  disagreeable  taste  or 
repellent  fluids  or  spines,  these  odious  qualities  being  frequently 
associated  with  warning  colors. 

Larvae  need  protection  also  against  adverse  climatal  conditions, 
especially  low  temperature  and  excessive  moisture.  The  thick  hairy 
clothing  of  some  hibernating  caterpillars,  as  Isia  isabella,  doubtless 
serves  to  mollify  sudden  changes  of  temperature.  Naked  cutworms 
hibernate  in  well-sheltered  situations,  and  the  grubs  of  the  common 
"May  beetles,"  or  "June  bugs,"  burrow  down  into  the  ground  below 
the  reach  of  frost.  Ordinary  high  temperatures  have  little  effect  upon 
larvae,  except  to  accelerate  their  growth.  Excessive  moisture  is  fatal 
to  immature  insects  in  general — conspicuously  fatal  to  the  chinch  bug, 
Rocky  Mountain  locust,  aphids  and  sawfly  larvae.  The  effect  of  mois- 
ture may  be  an  indirect  one,  however;  thus  moisture  may  favor  the 
development  of  bacteria  and  fungi,  or  a  heavy  rain  may  be  disastrous 
not  only  by  drowning  larvae,  but  also  by  washing  them  off  their  food 
plants. 

As  a  result  of  secondary  adaptive  modifications,  larvae  may  differ 
far  more  than  their  imagines.  Thus  Platygaster  in  its  extraordinary  first 
larval  form  (Fig.  221)  is  entirely  unlike  the  larvae  of  other  parasitic 
Hymenoptera,  reminding  one,  indeed,  of  the  crustacean  Cyclops  rather 
than  the  larva  of  an  insect.  As  Lubbock  has  said,  the  characters  of  a 
larva  depend  (i)  upon  the  group  of  insects  to  which  the  larva  belongs 
and  (2)  upon  the  special  environment  of  the  larva. 

Pupa. — The  term  pupa  is  strictly  applicable  to  holometabolous 
insects  only.  Most  Lepidoptera  and  many  Diptera  have  an  obtect 
pupa  (Fig.  215),  or  one  in  which  the  appendages  and  body  are  compactly 
united;  as  distinguished  from  the  free  pupa  of  Neuroptera,  Trichoptera, 


DEVELOPMENT 


147 


Coleoptera  and  others,  in  which  the  appendages  are  free  (Fig.  206); 
but  this  distinction  cannot  always  be  drawn  sharply.  Diptera  present 
also  the  coarctate  type  of  pupa  (Fig.  207),  in  which  the  pupa  remains 
enclosed  in  the  old  larval  skin,  or  puparium. 

Pupal  characters,  though  doubtless  of  great  adaptive  and  phylogene- 
tic  significance,  have  received  but  little  attention.  Lepidopterous  pupae 
present  many  puzzling  characters,  for  example,  an  eye-like  structure 
(Fig.  216)  suggesting  an  ancestral  active  condition,  such  as  still  occurs 
among  heterometabolous  insects. 


Fig.  215. — Obtect 
pupa  of  milkweed  but- 
terfly, Anosia  plexip- 
pus,  natural  size. 


Pig.  216. — Head 
of  chrysalis  of  Pa- 
pilio  polyxenes,  to 
show  eye-like  struc- 
ture.    Enlarged. 


Pupation  of  a  Caterpillar.— The  process  of  pupation  in  a  caterpillar 
has  been  carefully  observed  by  Riley.  The  caterpillar  of  the  milkweed 
butterfly  (PI.  I,  ^)  spins  a  mass  of  silk  in  which  it  entangles  its  suranal 
plate  and  anal  prolegs  and  then  hangs  downward,  bending  up  the  ante- 
rior part  of  the  body  (B) ,  which  gradually  becomes  swollen.  The  skin  of 
the  caterpillar  splits  dorsally  from  the  head  backward,  and  is  worked 
back  toward  the  tail  (C  and  D)  by  the  contortions  of  the  larva. 

The  way  in  which  the  pupa  becomes  attached  to  its  silken  support 
is  rather  complex.  Briefly,  while  the  larval  skin  still  retains  its  hold  on 
the  support,  the  posterior  end  of  the  pupa  is  withdrawn  from  the  old 
integument  while  the  latter  is  being  temporarily  gripped  between  two 
of  the  abdominal  segments  of  the  pupa,  and  by  the  vigorous  whirling 
and  twisting  of  the  body  the  hooks  of  the  terminal  cremaster  of  the  pupa 
are  entangled  in  the  silken  support.  At  first  the  pupa  is  elongate  (£) 
and  soft,  but  in  an  hour  or  so  it  has  contracted,  hardened,  and  assumed 
its  characteristic  form  and  coloration  (F). 

Pupal  Respiration. — Except  under  special  conditions,  pupse  breathe 
by  means  of  ordinary  abdominal  spiracles.     Aquatic  pupae  have  special 


148  ^  ENTOMOLOGY 

respiratory  organs,  such  as  the  tracheal  fi.\a.ments  of  Si mulium  (Fig.  233), 
and  the  respiratory  tubes  of  Culex  (Fig.  232). 

Pupal  Protection. — Inactive  and  helpless,  most  pupae  are  concealed 
in  one  way  or  another  from  the  observation  of  enemies  and  are  pro- 
tected from  moisture,  sudden  changes  of  temperature,  mechanical  shock 
and  other  adverse  influences.  The  larvae  of  many  moths  burrow  into 
the  ground  and  make  an  earthen  cell  in  which  to 
pupate;  a  large  number  of  coleopterous  larvae  {Lach- 
A  nosterna,  Osmoderma,  Passalus,  Lucanus,  etc.)  make 

^^  a  chamber  in  earth  or  wood,  the  walls  of  the  cells 

^^m  being  strengthened  with  a  cementing  fluid  or  more  or 

^~"'-J  less  silk,  forming  a  rude  cocoon.     Silken  cocoons  are 

fljjB  spun  by  some  Neuroptera  (Chrysopidae,  Fig.   217),. 

^Hv  by  Trichoptera  (whose  cases  are  essentially  cocoons), 

^Mf  Lepidoptera,    a    few   Coleoptera   (as   Curculionidae, 

^  Donacia) ,  some  Diptera  (as  Itonididae) ,  Siphonaptera, 

and  many  Hymenoptera  (for  example,  Tenthredi- 

^^'^-    217— Co-     nidae,  Ichneumonidae,  wasps,  bees  and  some  ants). 

coon    of     Chrysopa,  .  . 

after  emergence  of  The  cocoon-making  instinct  is  most  highly  devel- 

largf  d.  ^^  ^  ^  ^^"  oped  in  Lepidoptera  and  the  most  elaborate  cocoons 
are  those  of  Saturniidae.  The  cocoon  of  Samia 
cecropia  is  a  tough,  water-proof  structure  and  is  double  (Fig.  218), 
there  being  two  air  spaces  around  the  pupa;  thus  the  pupa  is  pro- 
tected against  moisture  and  sudden  changes  of  temperature  and  from 
most  birds  as  well,  though  the  downy  woodpecker  not  infrequently  punc- 
tures the  cocoon.  S.  cecropia  binds  its  cocoon  firmly  to  a  twig ;  Tropcea 
luna  and  Telea  polyphemus  spin  among  leaves,  and  their  cocoons  (with 
some  exceptions)  fall  to  the  ground;  Callosamia  promethea,  whose  cocoon 
is  covered  with  a  curved  leaf,  fastens  the  leaf  to  the  twig  with  a  wrapping 
of  silk,  so  that  the  leaf  with  its  burden  hangs  to  the  twig  throughout  the 
winter.  The  leaves  surrounding  cocoons  may  render  them  inconspicu- 
ous or  may  serve  merely  as  a  foundation  for  the  cocoon.  While  silk  and 
often  a  waterproof  gum  or  cement  form  the  basis  of  a  cocoon,  much 
foreign  material,  such  as  bits  of  soil  or  wood,  is  often  mixed  in;  the 
cocoons  of  many  common  Arctiidae,  as  Diacrisia  virginica  and  Isia 
Isabella,  consist  principally  of  hairs,  stripped  from  the  body  of  the 
larva. 

Butterflies  have  discarded  the  cocoon,  traces  of  which  occur  in 
Hesperiidae,  which  draw  together  a  few  leaves  with  a  scanty  supply  of 
silk  to  make  a  flimsy  substitute  for  a  cocoon.     Papilionid  and  pierid 


Successive  stages  in  the  pupation  of  the  milkweed  caterpillar,  Anosia  plexippus.     Natural 

size. 


DEVELOPMENT  15I 

pupae  are  supported  by  a  silken  girdle  (Fig.  29),  and  nymphalid  chrysa- 
lides hang  freely  suspended  by  the  tail  (Fig.  215). 

Cocoon-Spinning. — The  caterpillar  af  Telea  polyphemus  "feels  with 
its  head  in  all  directions,  to  discover  any  leaves  to  which  to  attach  the 
fibres  that  are  to  give  form  to  the  cocoon.  If  it  finds  the  place  suitable, 
it  begins  to  wind  a  layer  of  silk  around  a  twig,  then  a  fibre  is  attached  to 
a  leaf  near  by,  and  by  many  times  doubling  this  fibre  and  making  it 
shorter  every  time,  the  leaf  is  made  to  approach  the  twig  at  the  distance 
necessary  to  build  the  cocoon;  two  or  three  leaves  are  disposed  like  this 
one  and  then  the  fibres  are  spread  between  them  in  all  directions,  and 
soon  the  ovoid  form  of  the  cocoon  distinctly  appears.     This  seems  to 


Fig. 


-Cocoon  of  Samia  cecropia,  cut  open  to  show  the  two  silken  layers  and  the 
enclosed  pupa.     Natural  size. 


be  the  most  difiicult  feat  for  the  worm  to  accompHsh,  as  after  this  the 
work  is  simply  mechanical,  the  cocoon  being  made  of  regular  layers 
of  silk  united  by  a  gummy  substance.  The  silk  is  distributed  in 
zigzag  lines  about  one-eighth  of  an  inch  long.  When  the  cocoon  is 
made,  the  worm  will  have  moved  his  head  to  and  fro,  in  order  to  distrib- 
ute the  silk,  about  two  hundred  and  fifty-four  thousand  times.  After 
about  half  a  day's  work,  the  cocoon  is  so  far  completed  that  the  worm 
can  hardly  be  distinguished  through  the  fine  texture  of  the  wall;  then 
a  gummy  resinous  substance,  sometimes  of  a  light  brown  color,  is  spread 
over  all  the  inside  of  the  cocoon.  The  larva  continues  to  work  for  four 
or  five  days,  hardly  taking  a  few  minutes  of  rest,  and  finally  another 
coating  is  spun  in  the  interior,  when  the  cocoon  is  all  finished  and  com- 
pletely air  tight.  The  fibre  diminishes  in  thickness  as  the  completion 
of  the  cocoon  advances,  so  that  the  last  internal  coating  is  not  half  so 
thick  and  so  strong  as  the  outside  ones."     (Trouvelot.) 


152  ENTOMOLOGY 

Emergence  of  Pupa. — Subterranean  pupae  wriggle   their  way  to 

the  surface  of  the  ground,  often  by  the  aid  of  spines  (Fig.  219),  that 

catch  successively  into  the  surrounding  soil.     These  locomotor  spines 

may  occur  on  almost  any  part  of  the  pupa,  but  occur  commonly  on  the 

abdominal  segments,  as  in  lepidopterous  pupae;  the 

t  extremity  of  the   abdomen,  also,   bears   frequently 

one  or  more  spinous  projections,  as  in  TipuHdae, 
Carabidae  and  Lepidoptera,  to  assist  the  escape  of 
the  pupa.  These  structures  are  found  also  in  pupae, 
as  those  of  Sesiidae,  that  force  their  way  out  of  the 
stems  of  plants  in  which  the  larvae  have  lived.  The 
emergence  from  the  cocoon  is  accomplished  in  some 
•  cases  by  the  pupa,  in  others  by  the  imago.  Hemero- 
^  biidae,  Trichoptera  and  the  primitive  lepidopteron 

Fig.  219.— Sub-     Eriocephala  use  the  pupal  mandibles  to  cut  an  open- 

terranean    pupa    of       _  _    -^  ^     _  ^  ^ 

Anisoia.  Enlarged,  ing  in  the  cocoou;  whilc  many  lepidopterous  pupae 
have  on  the  head  a  beak  for  piercing  the  cocoon,  or 
teeth  for  rending  or  cutting  the  silk. 

Eclosion. — During  the  last  few  hours  before  the  emergence  of  a 
butterfly  the  colors  of  the  imago  develop  and  may  be  seen  through  the 
transparent  skin  of  the  chrysalis  (PI.  11  A).  No  movement  occurs,  how^- 
eyer,  until  several  seconds  before  emergence;  then,  after  a  few  convul- 
sive movements  of  the  legs  and  thorax  of  the  imprisoned  insect,  the 
pupa  skin  breaks  in  the  region  of  the  tongue  and  legs  {B),  a  secondary 
split  often  occurs  at  the  back  of  the  thorax,  and  the  butterfly  emerges 
iC~E)  with  moist  body,  elongated  abdomen  and  miniature  wings. 
Hanging  to  the  empty  pupa  case  (F),  or  to  some  other  available  sup- 
port, the  insect  dries  and  its  wings  gradually  expand  (G,  H)  through  the 
pressure  of  the  blood.  At  regular  intervals  the  abdomen  contracts 
and  the  wings  fan  the  air,  and  sooner  or  later  a  drop  or  two  of  a  dull 
greenish  fluid  (the  meconium)  is  emitted  from  the  alimentary  canal. 
The  expansion  of  the  wings  takes  place  rapidly,  and  in  less  than  an 
hour,  as  a  rule,  they  have  attained  their  full  size  (/). 

T.  polyphemus  is  "provided  with  two  glands  opening  into  the  mouth, 
which  secrete  during  the  last  few  days  of  the  pupa  state,  a  fluid  which  is 
a  dissolvent  for  the  gum  so  firmly  uniting  the  fibres  of  the  cocoon.  This 
liquid  is  composed  in  great  part  of  bombycic  acid.  When  the  insect  has 
accomplished  the  work  of  transformation  which  is  going  on  under  the 
pupa  skin,  it  manifests  a  great  activity,  and  soon  the  chrysahs  covering 
bursts  open  longitudinally  upon  the  thorax;  the  head  and  legs  are  soon 


Successive  stages  in  the  emergence  of  the  milkweed  butterfly,  Anosia  plexippus,  from  the 
chrysalis.     Natural  size. 


DEVELOPMENT  1 55 

disengaged,  and  the  acid  fluid  flows  from  its  mouth,  wetting  the  inside  of 
the  cocoon.  The  process  of  exclusion  from  the  cocoon  lasts  for  as  much 
as  half  an  hour.  The  insect  seems  to  be  instinctively  aware  [?]  that 
some  time  is  required  to  dissolve  the  gum,  as  it  does  not  make  any  at- 
tempt to  open  the  fibres,  and  seems  to  wait  with  patience  this  event. 
When  the  liquid  has  fully  penetrated  the  cocoon,  the  pupa  contracts  its 
body,  and  pressing  the  hinder  end,  which  is  furnished  with  little  hooks, 
against  the  inside  of  the  cocoon,  forcibly  extends  its  body;  at  the  same 
time  the  head  pushes  hard  upon  the  fibres  and  a  little  swelling  is 
observed  on  the  outside.  These  contractions  and  extensions  of  the 
body  are  repeated  many  times,  and  more  fluid  is  added  to  soften  the 
gum,  until  under  these  efforts  the  cocoon  swells,  and  finally  the  fibres 
separate,  and  out  comes  the  head  of  the  moth.  In  an  instant  the  legs 
are  thrust  out,  and  then  the  whole  body  appears;  not  a  fibre  has  been 
broken,  they  have  only  been  separated. 

"To  observe  these  phenomena,  I  had  cut  open  with  a  razor  a  small 
portion  of  a  cocoon  in  which  was  a  living  chrysalis  nearly  ready  to  trans- 
form. The  opening  made  was  covered  with  a  piece  of  mica,  of  the  same 
shape  as  the  aperture,  and  fixed  to  the  cocoon  with  mastic  so  as  to  make 
it  solid  and  air-tight;  through  the  transparent  mica  I  could  see  the  move- 
ments of  the  chrysalis  perfectly  well. 

''When  the  insect  is  out  of  the  cocoon,  it  immediately  seeks  for  a 
suitable  place  to  attach  its  claws,  so  that  the  wings  may  hang  down,  and 
by  their  own  weight  aid  the  action  of  the  fluids  in  developing  and 
unfolding  the  very  short  and  small  pad-like  wings.  Every  part  of  the 
insect  on  leaving  the  cocoon,  is  perfect  and  with  the  form  and  size  of 
maturity,  except  the  pad-like  wings  and  swollen  and  elongated  abdomen, 
which  still  gives  the  insect  a  worm-like  appearance;  the  abdomen  con- 
tains the  fluids  which  flow  to  the  wings. 

"When  the  still  immature  moth  has  found  a  suitable  place,  it  re- 
mains quiet  for  a  few  minutes,  and  then  the  wings  are  seen  to  grow  very 
rapidly  by  the  afiiux  of  the  fluid  from  the  abdomen.  In  about  twenty 
minutes  the  wings  attain  their  full  size,  but  they  are  still  like  a  piece  of 
wet  cloth,  without  consistency  and  firmness,  and  as  yet  entirely  unfit  for 
flight,  but  after  one  or  two  hours  they  become  sufficiently  stiff,  assuming 
the  beautiful  form  characteristic  of  the  species"  (Trouvelot).  The 
expansion  of  the  wing  is  due  to  blood-pressure  brought  about  chiefly  by 
the  abdominal  muscles.  In  the  freshly-emerged  insect,  the  two  mem- 
branes of  the  wing  are  corrugated,  and  expansion  consists  in  the  flatten- 
ing out  of  these  folds.     The  wing  is  a  sac,  which  would  tend  to  enlarge 


150  ENTOMOLOGY 

into  a  balloon-shaped  bag,  were  it  not  for  hypodermal  fibres  which  hold 
the  wing-membranes  closely  together  (Mayer).  Tropcea  luna  and 
Philosamia  cynthia  cut  and  force  an  opening  through  the  cocoon  by 
means  of  a  pair  of  saw-like  organs,  one  at  the  base  of  each  front  wing. 

The  cocoons  of  Samia  cecropia  and  Callosamia  promethea  do  not 
have  a  gummy  coating  over  the  entire  interior.  In  each  case  the  end 
through  which  the  moth  emerges  is  composed  of  silken  fibres  loosely 
pulled  together  and  not  covered  with  a  gummy  substance.  It  is  as  if 
each  layer  of  the  cocoon  was  spun  into  a  fringe  at  this  end,  the  fringes 
of  all  layers  being  bunched  together  forming  a  Httle  cone.  Jn  the  co- 
coon of  Samia  cecropia,  it  is  possible  to  push  a  pencil  through  this 
fringe  with  apparently  no  effort.  The  fibres  part  readily,  it  being  neces- 
sary to  break  only  a  few  in  the  extreme  outside  layer.  The  same  can 
be  said  of  the  cocoon  of  C.  promethea  (H.  B.  Weiss). 

The  temperature  inside  a  cocoon  is  practically  the  same  as  that  of  the 
surrounding  air,  there  being  a  constant  tendency  for  the  inside  tem- 
perature to  approach  that  of  its  surroundings.  Sudden  changes  of 
temperature  do  not  occur  within  a  cocoon.  When  the  outside  tem- 
perature is  suddenly  lowered,  as  from  io°  C  to  o°  C,  the  temperature  in 
a  cocoon  falls  gradually,  and  even  during  a  gradual  rise  the  cocoon- 
temperature  lags  behind  that  of  its  surroundings,  on  account  of  the  poor 
conducting  qualities  of  air  and  silk  (H.  B.  Weiss). 

Hypermetamorphosis. — In  a  few  remarkable  instances,  metamor- 
phosis involves  more  than  three  stages,  owing  to  the  existence  of  super- 
numerary larval  forms.  This  phenomenon  of  hypermetamorphosis 
occurs  notably  in  the  coleopterous  genera  Melo'e,  Epicauta,  Sitaris 
and  Rhipiphorus,  in  Strepsiptera  and  in  several  parasitic  Hymenoptera. 

In  the  oil-beetle,  Melo'e,  as  described  by  Riley,  the  newly-hatched 
larva  {triungulin)  is  active  and  campodea-form.  It  climbs  upon  a 
flower  and  thence  upon  the  body  of  a  bee  {Anthophora) ,  which  carries 
it  to  the  nest,  where  it  eats  the  egg  of  the  bee.  After  a  molt,  the  larva 
though  still  six-legged,  has  become  cylindrical,  fleshy  and  less  active, 
resembling  a  lamellicorn  larva;  it  now  appropriates  the  honey  of  the  bee. 
With  plenty  of  rich  food  at  hand  the  larva  becomes  sluggish,  and  after 
another  molt  appears  as  a  pseudo-pupa,  with  functionless  mouth 
parts  and  atrophied  legs.  From  this  pseudo-pupa  emerges  a  third 
larval  form,  of  the  pure  cruciform  type,  fat  and  apodous  like  the  bee- 
larvae  themselves.  After  these  four  distinct  stages  the  larva  becomes 
a  pupa  and  then  a  beetle. 

Epicauta,  another  meloid,  has  a  similar  history.     The  triungulin 


DEVELOPMENT 


:57 


(Fig.  220,  A)  of  E.  vittata  burrows  into  an  egg-pod  of  Melanoplus  differ- 
entialis  and  eats  the  eggs  of  that  grasshopper.  After  a  molt  the  second 
larva  {carabidoid  form)  appears;  this  (B)  is  soft,  with  reduced  legs  and 
mouth  parts  and  less  active  than  the  triungulin.  A  second  molt  and 
the  scarabceidoid  form  of  the  second  larva  is  assumed;  the  legs  and  mouth 
parts  are  now  rudimentary  and  the  body  more  compact  than  before. 
A  third  and  a  fourth  molt  occur  with  little  change  in  the  form  of  the 
second  larva,  which  is  now  in  its  ultimate  stage  (C) .  After  the  fifth 
molt,  however,  the  coarctate  larva,  or  pseudo-pupa,  appears;  this  {D) 
hibernates  and  in  spring  sheds  its  skin  and  becomes  the  third  larva, 


Fig.  220. — Stages  in  the  hypermetamorphosis  of  Epicauta.  A,  triungulin;  B,  carabi- 
doid stage  of  second  larva;  C,  ultimate  stage  of  second  larva;  D,  coarctate  larva;  E,  pupa;  F, 
imago.  E  is  species  cinerea;  the  others  are  viltata.  All  enlarged  except  F. — After  Riley, 
from  Trans.  St.  Louis  Acad.  Science. 


which  soon  transforms  to  a  true  pupa  (£),  from  which  the  beetle  (F) 
shortly  emerges.  Thus  the  pupal  stage  is  preceded  by  at  least  three 
distinct  larval  stages. 

Strepsiptera,  the  subject  of  two  important  volumes  by  Dr.  W.  D. 
Pierce,  are  all  hypermetamorphic.  These  parasites  affect  almost 
exclusively  Hymenoptera  and  Homoptera,  causing  the  "stylopized" 
condition  known  to  collectors  of  bees,  wasps  or  bugs,  in  which  the  pres- 
ence of  the  parasite  is  indicated  by  a  flat  disk-like  plate  (in  the  female 
parasite)  or  a  tuberculate  rounded  projection  (male)  protruding  from 
between  segments  of  the  abdomen.  The  male  is  winged  but  the  female 
is  maggot-like  and  sedentary,  a  mere  sac  of  eggs,  often  two  thousand 
or  more  in  number,  which  hatch  inside  the  body  of  the  mother  into  active 
little  hexapodous  thysanuriform  larvae  known  as  triiingulinids .     These 


158 


ENTOMOLOGY 


are  probably  carried  by  the  host  to  flowers  or  other  places  where  they 
are  able  to  attach  themselves  to  the  bodies  of  their  future  hosts.  After 
penetrating  into  the  body  of  the  host  the  larva  grows  rapidly ;  with  the 
first  molt  the  eyes  and  legs  are  lost,  the  second  instar  being  scarabae- 
idoid  in  form;  after  the  second  molt  the  male  and  female  larvae  differ 
in  development. 

The  most  extraordinary  metamorphoses  have  been  found  among 
parasitic  Hymenoptera,  as  in  Platygaster,  a  proctotrypid  which  infests 
the  larva  of  Cecidomyia.     The  egg  of  Platygaster,  according  to  Ganin, 


Pig.  221. — Stages  in  the  hypermetamorphosis  of  Platygaster.  A,  first  larva;  B,  second 
larva;  C,  third  larva;  a,  antenna;  h,  brain;/,  fat-tissue;  h,  hind  intestine;  m,  mandible;  mo, 
mouth;  ms,  muscle;  w, nerve  cord;  r,  reproductive  organ  of  one  side;  s,  salivary  gland;  t, 
trachea. — After  Ganin. 


hatches  into  a  larva  of  bizarre  form  (Fig.  221,  A),  suggesting  the  crusta- 
cean Cyclops,  rather  than  an  insect.  This  first  larva  has  a  blind  food 
canal  and  no  nervous,  circulatory  or  respiratory  systems.  After  a 
molt  the  outHneis  oval  {B),  and  there  are  no  appendages  as  yet,  though 
the  nervous  system  is  partially  developed.  Another  molt,  and  the 
third  larva  appears  (C),  elHptical  in  contour,  externally  segmented,  with 
tracheae  and  a  pair  of  mandibles.  From  now  on,  the  development  is 
essentially  like  that  of  other  parasitic  Hymenoptera. 

Equally  anomalous  are  the  changes  undergone  by  Polynema,  a  proc- 
totrypid parasite  in  the  eggs  of  dragon  flies,  and  by  the  proctotrypid 
Teleas,  which  affects  the  eggs  of  the  tree  cricket  {(Ecanthus).  In  all 
these  cases  the  larvae  go  through  changes  which  in  most  other  insects  are 
confined  to  the  egg  stage.  In  other  words,  the  larva  hatches  before  its 
embryonic  development  is  completed,  so  to  speak. 


DEVELOPMENT  159 

Significance  of  Metamorphosis. — "The  essential  features  of  meta- 
morphosis," says  Sharp,  "appear  to  be  the  separation  in  time  of  growth 
and  development  and  the  limitation  of  the  reproductive  processes  to  a 
short  period  at  the  end  of  the  individual  life." 

The  simplest  insects,  Thysanura,  have  no  metamorphosis,  and  show 
no  traces  of  ever  having  had  one.  Hence  it  is  inferred  that  the  first 
insects  had  none;  in  other  words,  the  phenomenon  of  metamorphosis 
originated  later  than  insects  themselves.  Successive  stages  in  the 
evolution  of  metamorphosis  are  illustrated  in  the  various  orders  of 
insects. 

The  distinctive  mark  of  the  simplest  metamorphosis,  as  in  Orthop- 
tera  and  Hemiptera,  is  the  acquisition  of  wings;  growth  and  sexual 
development  proceeding  essentially  as  in  the  non-metamorphic  insects 
(Thysanura  and  Collembola) .  Here  the  development  of  wings  does  not 
interfere  with  the  activity  of  the  insect;  its  food  habits  remain  unaltered; 
throughout  life  the  environment  of  the  individual  is  practically  the  same. 
Even  when  considerable  difference  exists  between  the  nymphal  and 
imaginal  environments,  as  in  Ephemerida  and  Odonata,  the  activity  of 
the  individual  may  still  be  continuous,  even  if  somewhat  lessened  as  the 
period  of  transformation  approaches. 

With  Neuroptera,  the  pupal  stage  appears.  In  these  and  all  other 
holometabolous  insects  the  larva  accumulates  a  surplus  of  nutriment 
sufficient  for  the  further  development,  which  becomes  condensed  into 
a  single  pupal  stage,  during  which  external  activity  ceases  temporarily. 

With  the  increasing  contrast  between  the  organization  of  the  larva 
and  that  of  the  imago,  the  pupal  stage  gradually  becomes  a  necessity. 
Metamorphosis  now  means  more  than  the  mere  acquisition  of  wings,  for 
the  larva  and  the  imago  have  become  adapted  to  widely  different  en- 
vironments, chiefly  as  regards  food.  The  caterpillar  has  biting  mouth 
parts  for  eating  leaves,  while  the  adult  has  sucking  organs  for  obtaining 
liquid  nourishment;  the  maggot,  surrounded  by  food  that  may  be  ob- 
tained almost  without  exertion,  has  but  minimum  sensory  and  locomotor 
powers  and  for  mouth  parts  only  a  pair  of  simple  jaws;  as  contrasted 
with  the  fly,  which  has  wings,  highly  developed  mouth  parts  and  sense 
organs,  and  many  other  adaptations  for  an  environment  which  is 
strikingly  unKke  that  of  the  larva;  so  also  in  the  case  of  the  higher 
Hymenoptera,  where  maternal  or  family  care  is  responsible  for  the  help- 
less condition  of  the  larva. 

Thus  it  is  evident  that  the  change  from  larval  to  imaginal  adapta- 
tions is  no  longer  congruous  with  continuous  external  activity;  a  quies- 


l6o  ENTOMOLOGY 

cent  period  of  reconstruction  becomes  inevitable  (though  this  statement 
does  not,  of  course,  explain  anything). 

As  was.  said,  the  cruciform  type  of  larva  has  been  derived  from  the 
thysanuriform  type,  the  strongest  evidence  of  this  being  the  fact  that 
among  hypermetamorphic  insects,  the  change  from  the  one  to  the  other 
takes  place  during  the  lifetime  of  the  individual.  Furthermore,  the 
cruciform  condition  is  plainly  an  adaptive  one,  brought  about  by  an 
abundant  and  easily  obtainable  supply  of  food.  The  lack  of  a  thysanuri- 
form stage  in  the  development  of  the  most  specialized  cruciform  larvae, 
as  those  of  flies  and  bees,  is  regarded  by  Hyatt  and  Arms  as  an  illustra- 
tion of  the  general  principle  known  as  "acceleration  of  development," 
according  to  which  newer  and  useful  adaptive  characters  tend  to  appear 
earlier  and  earlier  in  the  development,  gradually  crowding  upon  and 
forcing  out  older  and  useless  characters.  In  connection  with  this  sub- 
ject, the  appearance  of  temporary  abdominal  legs  in  embryo  bees  is 
significant,  as  indicating  an  ancestral  active  condition.  In  accounting 
for  the  evolution  of  metamorphosis,  the  theory  of  natural  selection  finds 
one  of  its  most  important  applications. 

3.  Internal  Metamorphoses 

In  Heterometabola,  the  internal  post-embryonic  changes  are  as  di- 
rect as  the  external  changes  of  form;  in  Holometabola,  on  the  contrary, 
not  all  the  larval  organs  pass  directly  into  imaginal  organs,  for  certain 
larval  tissues  are  demolished  and  their  substance  reconstructed  into 
imaginal  tissues.  When  indirect,  the  internal  metamorphosis  is 
nevertheless  continuous  and  gradual,  without  the  abruptness  that 
characterizes  the  external  transformation.  In  the  larval  stage  imaginal 
organs  arise  and  grow;  in  the  pupal  stage  the  purely  larval  organs 
gradually  disappear  while  the  imaginal  organs  are  continuing  their 
development. 

Phagocytes.^The  destruction  of  larval  tissues,  or  histolysis,  is  due 
often  to  the  amoeboid  blood  corpuscles,  known  as  leucocytes  or  phago- 
cytes, which  attack  some  tissues  and  absorb  their  material,  but  later 
are  themselves  food  for  the  developing  imaginal  tissues.  The  construc- 
tion of  tissues  is  termed  histogenesis. 

In  Coleoptera  the  degeneration  of  the  larval  muscles  is  entirely 
chemical,  there  being  no  evidence  of  phagocytosis,  according  to  Dr. 
R.  S.  Breed.  Berlese,  indeed,  goes  so  far  as  to  deny  in  general  the 
destructive  action  of  leucocytes  on  larval  tissues. 


DEVELOPMENT 


l6l 


Imaginal  Buds. — The  wings  and  legs  of  a  fly  originate  in  the  larva 
in  the  form  of  cellular  masses,  termed  imaginal  buds,  or  histoblasts,  as 
Weismann  discovered.  Thus  in  the  larva  of  Corethra,  there  are  in 
each  thoracic  segment  a  pair  of  dorsal  buds  and  a  pair  of  ventral  buds 
(Fig.  222),  each  bud  being  clearly  an  evagination  of  the  hypodermis 
at  the  bottom  of  a  previous  invagination.  The  six  ventral  buds  form 
the  legs  eventually;  of  the  dorsal  buds,  the  middle  and  posterior  pairs 
form,  respectively,  the  wings  and  the  halteres,  and  the  anterior  pair 


Fig.  222. — Diagram- 
matic transverse  section  of 
Corethra  larva,  to  show 
imaginal  buds  of  wings  (w) 
and  legs  (I);  h,  hypoder- 
mis; i,  integument. — Modi- 
fied from  Lang's  Lehrbuch. 


C  D 

Pig.  223. — Diagrammatic  t-ransverse  sections  of  muscid 
larvae,  to  show  imaginal  buds,  h,  larval  hypodermis;  i,  larval 
integument;  ih,  imaginal  hypodermis;  I,  imaginal  bud  of  leg; 
w,  imaginal  bud  of  wing. — Modified  from  Lang's  Lehrbuch. 


form  the  pupal  respiratory  processes.  Each  imaginal  bud  is  situated  in 
a  peripodal  cavity,  the  wall  of  which  (peripodal  membrane)  is  continu- 
ous with  the  general  hypodermis;  as  the  legs  and  wings  develop,  they 
emerge  from  their  peripodal  sacs  and  become  free. 

In  Corethra  but  little  histolysis  occurs,  most  of  the  larval  structures 
passing  directly  into  the  corresponding  structures  of  the  adult.  Core- 
thra is,  indeed,  in  many  respects  intermediate  between  heterometabo- 
lous  and  holometabolous  insects  as  regards  its  internal  changes. 

Muscidae. — In  Muscidae,  as  compared  with  Corethra,  the  imaginal 
buds  are  more  deeply  situated,  the  peripodal  membrane  forming  a 


l62 


ENTOMOLOGY 


stalk  (Fig.  223),  and  the  processes  of  histolysis  and  histogenesis  become 
extremely  complicated.  The  hypodermis,  muscles,  alimentary  canal 
and  fat-body  are  gradually  broken  down  and  remodeled,  and  part  of 
the  respiratory  system  is  reorganized,  though  the  dorsal  vessel  and  the 

central  nervous  system,  uninterrupted  in 
their  functions,  undergo  comparatively 
little  alteration. 

The  imaginal  hypodermis  of  the  tho- 
rax arises  from  thickenings  of  the  peri- 
podal  membrane  which  spread  over  the 
larval  hypodermis,  while  the  latter  is 
gradually  being  broken  down  by  the 
leucocytes;  in  the  head  and  abdomen 
the  process  is  essentially  the  same  as  in 
the  thorax,  the  new  hypodermis  arising 
from  imaginal  buds. 

Most  of  the  larval  muscles,  excepting 
the  three  pairs  of  respiratory  muscles, 
undergo  dissolution.  The  imaginal 
muscles  have  been  traced  back  to  meso- 
dermal cells  such  as  are  always  associated 
with  imaginal  buds. 

Hymenoptera  and  Lepidoptera. — 
The  internal  transformation  in  Hymen- 
optera, according  to  Bugnion,  is  less  pro- 
found than  in  Muscidae  and  more  exten- 
sive than  in  Coleoptera  and  Lepidoptera. 
The  internal  metamorphosis  in  Lepidop- 
tera resembles  in  many  respects  that  of 
Corethra.  In  both  these  orders  the  dorsal 
pair  of  prothoracic  buds  is  absent.  In 
a  full-grown  caterpillar  the  fundaments  of  the  imaginal  legs  and 
wings  (Fig.  224)  may  be  seen,  the  wings  in  a  frontal  section  of  the 
larva  appearing  as  in  Fig.  225.  Many  of  the  details  of  the  internal 
metamorphosis  in  Lepidoptera  have  been  described  by  Newport  and 
Gonin.  Figure  226,  after  Newport,  shows  some  of  the  more  evi- 
dent internal  differences  in  the  larva,  pupa  and  imago  of  a  lepidop- 
terous  insect. 

Significance  of  Pupal  Stage. — To  repeat — among  holometabolous 
insects  the  function  of  nutrition  becomes  relegated  to  the  larval  stage 


Pig.  224. — Imaginal  buds  of  full 
grown  larva  of  Pieris,  dorsal  aspect. 
b,  brain;  m,  mid  intestine;  s^,  pro- 
thoracic  spiracle;  s*,  first  abdominal 
spiracle;  sg,  silk  gland;  /,  pro- 
thoracic  bud;  II,  bud  of  fore  wing; 
III,  bud  of  hind  wing. — After 
Gonin. 


DEVELOPMENT 


163 


"^iSsiuiuiin^j^ 


Fig.  225. — Section  through  left  hind  wing  in  larva  of  Pieris  rapce,  the  section  being  a 
frontal  one  of  the  caterpillar;  the  base  of  the  wing  is  anterior  in  position,  and  the  apex 
posterior,     c,  cuticula;  //,  hypodermis;  t,  trachea;  w,  developing  wing. — After  Mayer. 


Pig.  226. — Internal  transformations  of  Sphinx  ligustri.  A,  larva;  B,  pupa;  C,  moth; 
a,  aorta;  an,  antenna;  b,  brain;  /,  fore  intestine;  fr,  food  reservoir;  h,  hind  intestine;  ht, 
heart;  tn,  mid  intestine;  mt,  Malpighian  tubes;  p.  proboscis;  s,  suboesophageal  ganglion; 
t,  testis;  tg,  thoracic  ganglia;  v,  ventral  nerve  cord. — After  Newport. 


I 64  ENTOMOLOGY 

and  that  of  reproduction  to  the  imaginal  stage.  Larva  and  imago 
become  adapted  to  widely  different  environments.  So  dissimilar 
are  the  two  environments  that  a  gradual  change  from  the  one  to  the 
other  is  no  longer  possible;  the  revolutionary  changes  in  structure 
necessitate  a  temporary  cessation  of  external  activity. 


CHAPTER  IV 

ADAPTATIONS  OF  AQUATIC  INSECTS 

Ease,  versatility  and  perfection  of  adaptation  are  beautifully  exem- 
plified in  aquatic  insects. 

Systematic  Position. — Aquatic  insects  do  not  form  a  separate  group 
in  the  system  of  classification,  but  are  distributed  among  several  orders, 
of  which  Plecoptera,  Ephemerida,  Odonata  and  Trichoptera  are  pre- 
eminently aquatic.  One  third  of  the  families  of  Heteroptera  and  less 
than  one  fourth  those  of  Diptera  are  more  or  less  aquatic.  One  tenth 
of  the  famihes  of  Coleoptera  frequent  the  water  at  one  stage  or  another, 
two  famihes  of  Neuroptera,  and  only  half  a  dozen  genera  of  Lepidoptera. 
A  few  Collembola  live  upon  the  surface  of  water;  and  several  Hymenop- 
tera,  though  not  strictly  aquatic,  are  known  to  parasitize  the  eggs  and 
larvae  of  aquatic  insects. 

The  change  from  the  terrestrial  to  the  aquatic  habit  has  been  a 
gradual  change  of  adaptation,  not  an  abrupt  one.  Thus  at  present  there 
are  some  tipulid  larv^  that  inhabit  comparatively  dry  soil;  others  live 
in  earth  that  is  moist;  many  require  a  saturated  soil  near  a  body  of 
water  and  many,  at  length,  are  strictly  aquatic  Among  beetles,  also, 
similar  transitional  stages  are  to  be  found. 

Food. — Insects  have  become  adapted  to  utilize  with  remarkable 
success  the  immense  and  varied  supply  of  food  that  the  water  affords. 
Hosts  of  them  attack  such  parts  of  plants  as  project  above  the  surface  of 
the  water,  and  the  caterpillar  of  Paraponyx  (Fig.  174)  feeds  on  sub- 
merged leaves,  especially  of  Vallisneria,  being  in  this  respect  almost 
unique  among  Lepidoptera.  Hydrophilid  beetles  and  many  other 
aquatic  insects  devour  submerged  vegetation.  The  larvae  of  the  chry- 
someHd  genus  Donacia  find  both  nourishment  and  air  in  the  roots  of 
aquatic  plants.  Various  Collembola  subsist  on  floating  alg^e,  and  larvae 
of  mosquitoes  and  black-flies  on  microscopic  organisms  near  the  surface, 
while  larvae  of  midges,  Chironomus,  find  food  in  the  sediment  that  accu- 
mulates at  the  bottom  of  a  body  of  water. 

Predaceous  species  abound  in  the  water.  The  backswimmer, 
Notonecta  (Fig.  227)  approaches  its  prey  from  beneath,  clasps  it  with 
the  front  pair  of  legs  and  pierces  it.     The  water  scorpions,  Nepa  and 

16s 


i66 


ENTOMOLOGY 


Ranatra,  likewise  have  prehensile  front  legs  along  with  powerful  piercing 
organs.  The  electric  light  bugs,  Belostoma  and  Benacus  (Fig.  23)  even 
kill  small  fishes  by  their  poisonous  punctures.  Some  other  kinds,  as  the 
water-skaters  (Gerridae,  Fig.  228),  depend  on  dead  or  disabled  insects. 
The  species  of  Eydrophilus  (Fig.  229)  are  to  some  extent  carnivorous  as 


Fig.  227.- — Backswimmer,   Notonecta 
lata,  natural  size. 


Pig.  228. 


-Water-skater,  Gerris  remigis, 
natural  size. 


larvae  but  phytophagous  as  imagines,  while  Dytiscidae  (diving  beetles) 
are  carnivorous  throughout  life.  Aquatic  insects  eat  not  only  other 
insects,  but  also  worms,  crustaceans,  mollusks  or  any  other  available 
animal  matter. 

Even  aquatic  insects  are  not  exempt  from  the  attacks  of  parasitic 
species.     A  few  Hymenoptera  actually  enter  the  water  to  find  their 
victims,  for  example,  the  ichneumon  Agriotypus, 
which  lays  its  eggs  on  the  larvae  of  caddis  flies. 

Locomotion. — Excellent  adaptations  for 
aquatic  locomotion  are  found  in  the  common 
Hydrophilus  triangularis  (Fig.  229).  Its  general 
form  reminds  one  of  a  boat,  and  its  long  legs 
resemble  oars.  The  smoothly  elHptical  contour 
and  the  polished  surface  serve  to  lessen  resistance. 
Owing  to  the  form  of  the  body  (Fig.  230,  A)  and 
the  presence  of  a  dorsal  air-chamber  under  the 
elytra,  the  back  of  the  insect  tends  to  remain 
uppermost,  while  in  the  backswimmer,  Notonecta 
(Fig.  230,  B),  on  the  other  hand,  the  conditions 
are  reversed,  and  the  insect  swims  with  its  back 
downward.  The  legs  of  Hydrophilus,  excepting  the 
first  pair,  are  broad  and  thin  (Fig.  231,  A)  and  the  tarsi  are  fringed  with 
long  hairs.  When  swimming,  the  "stroke"  is  made  by  the  flat  surface, 
aided  by  the  spreading  hairs;  but  on  the  "recover,"  the  leg  is  turned  so 


Fig.  229. — Hydroph- 
ilus triangularis,  nat- 
ural size. 


ADAPTATIONS    OF    AQUATIC    INSECTS 


167 


as  to  cut  the  water,  while  the  hairs  fall  back  against  the  tarsus  from  the 
resistance  of  the  water,  as  the  leg  is  being  drawn  forward.     The  hind 


A  B 

Fig.  230. — Transverse  sections  of   {A)   Hydrophilus  and   (B)   Nolonecla.     e,   elytron;   h, 
hemelytron;  I,  metathoracic  leg. 

legs,  being  nearest  the  center  of  gravity,  are  of  most  use  in  swimming, 
though  the  second  pair  also  are  used  for  this  purpose;  indeed,  a  terrestrial 
insect,  finding  itself  in  the 
water,  instinctively  relies 
upon  the  third  pair  of  legs 
for  1  ocomotion.  Hydro- 
philus uses  its  oar-like  legs 
alternately,  in  much  the 
same  sequence  as  land 
insects,  but  Cyhister  and 
other  Dytiscidas,  which 
are  even  better  adapted 
than  Hydrophilus  for 
aquatic  locomotion,  move 
the  hind  legs  simultane- 
ously, and  therefore  can 
swim  in  a  straight  line, 
without  the  wobbling  and 
less  economical  m  o  v  e- 
ments  that  characterize 
Hydrophilus. 

Larvae  of  mosquitoes 
propel  themselves  b  y 
means  of  lashing,  or  undu- 
latory,  movements  of  the 

abdomen.  A  peculiar  mode  of  locomotion  is  found  in  dragon  fly 
nymphs,  which  project  themselves  by  forcibly  ejecting  a  stream  of 
water  from  the  anus. 


Fig.  231. — Left  hind  legs  of  aquatic  beetles.  A, 
Hydrophilus  triangularis;  B,  Cybister  fimbriolatus;  c, 
coxa;  /,  femur;  s,  spur;  /,  tarsus;  ti,  tibia;  tr,  tro- 
chanter. 


i08 


ENTOMOLOGY 


On  account  of  the  large  amount  of  air  that  they  carry  about,  most 
aquatic  imagines  are  lighter  than  the  water  in  which  they  live,  and 
therefore  can  rise  without  effort,  but  can  descend  only  by  exertion,  and 
can  remain  below  only  by  clinging  to 
chance  stationary  objects.  The  mosquito 
larva  (Fig.  232,  ^)  is  often  heavier  than 
water,  but  the  pupa  (Fig.  232,  B)  is  lighter, 
and  remains  clinging  to  the  surface  film. 

The  tension  of  this  surface  film  is  suffi- 
cient to  support  the  weight  of  an  insect 
up  to  a  certain  limit,  provided  the  insect 
has  some  means  of  keeping  its  body  dry. 
This  is  accompKshed  usually  by  hairs, 
set  together  so  thickly  that  water  cannot 
penetrate  between  them.  As  the  legs  and 
body  of  Gerris  are  rendered  water-proof 
by  a  velvety  clothing  of  hairs,  the  insect, 
though  heavier  than  water,  is  able  to  skate 
about  on  the  surface.  Gyrinus,  by  means 
of  a  similar  adaptation,  can  circle  about 
on  the  surface  film,  and  minute  collembo- 
lans  leap  about  on  the  surface  as  readily 
as  on  land. 

The  modifications  of  the  legs  for  swim- 
ming have  often  impaired  their  usefulness 
for  walking,  so  that  many  aquatic  Coleop- 
tera  and  Hemiptera  can  move  but  awk- 
wardly on  land.  When  walking,  it  is  inter- 
esting to  note,  Cyhister  and  some  other 
aquatic  forms  no  longer  move  their  hind 
legs  simultaneously  as  they  do  in  swim- 
ming, but  use  them  alternately,  like  ter- 
restrial species. 

The  adaptations  for  swimming  do  not 
necessarily  affect  the  power  of  flight. 
Dytiscus,  Hydrophilus,  Gyrinus,  Notonecta,  Benacus  and  many  other 
Coleoptera  and  Hemiptera  leave  the  water  at  night  and  fly  around, 
often  being  found  about  electric  lights. 

Respiration. — Aquatic  insects  have  not  only  retained  the  primitive, 
or  open  {holopneustic)  type  of  respiration,  characterized  by  the  presence 


Fig.  232. — Larva  {A)  and  pupa 
{B)  of  mosquito,  Culex  pipiens. 
r,  respiratory  tube;  /,  tracheal 
gills. 


ADAPTATIONS    OF    AQUATIC    INSECTS  1 69 

of  spiracles,  but  have  also  developed  an  adaptive,  or  closed  (apneustic) 
type,  for  utilizing  air  that  is  mixed  with  water. 

Through  minor  modifications  of  structure  and  habit,  many  holo- 
pneustic  insects  have  become  fitted  for  an  aquatic  life.  In  these  in- 
stances the  insects  have  some  means  of  carrying  down  a  supply  of  air 
from  the  surface  of  the  water.  Thus  the  backswimmer,  Notonecta, 
bears  on  its  body  a  silvery  film  of  air  entangled  in  closely  set  hairs, 
which  exclude  the  water.  The  whirhgig  beetle,  Gyrinus,  descends 
with  a  bubble  of  air  at  the  end  of  the  abdomen.  Dytiscus  and  Hydro- 
philus  have  each  a  capacious  air-space  between  the  elytra  and  the 
abdomen,  into  which  space  the  spiracles  open.  The  water  scorpions, 
Nepa  and  Ranatra,  have  each  a  long  respiratory  organ  composed  of  two 
valves,  which  lock  together  to  form  a  tube  that  communicates  with  the 
single  pair  of  spiracles  situated  near  the  end  of  the  abdomen.  The 
mosquito  larva,  hanging  from  the  surface  film,  breathes  through  a 
cyhndrical  tube  (Fig.  232,  A,  r)  projecting  from  the  penultimate 
abdominal  segment;  the  pupa,  however,  bears  a  pair  of  respiratory 
tubes  on  the  back  of  the  thorax  (Fig.  232,  B,  r,  r),  which  is  now  upward, 
probably  in  order  to  facilitate  the  escape  of  the  fly.  The  rat-tailed 
maggot  (Eristalis),  three  quarters  of  an  inch  long,  has  an  extensile 
caudal  tube  seven  times  that  length,  containing  two  tracheae  terminating 
in  spiracles,  through  which  air  is  brought  down  from  above  the  mud  in 
which  the  larva  lives.  Similarly,  in  the  dipterous  larva,  Bitlacomor pha 
clavipes  (Fig.  175),  the  posterior  segments  of  the  abdomen  are  attenu- 
ated to  form  a  long  respiratory  tube.  The  larva  of  Donacia  appears 
to  have  no  special  adaptations  for  aquatic  respiration  except  a  pair  of 
spines  near  the  end  of  the  body,  for  piercing  air  chambers  in  the  roots 
of  the  aquatic  plants  in  which  it  dwells. 

The  simplest  kind  of  apneustic  respiration  occurs  in  aquatic  nymphs 
such  as  those  of  Ephemerida  and  Agrionidae,  whose  skin  at  first  is  thin 
enough  to  allow  a  direct  aeration  of  the  blood.  This  cutaneous  res- 
piration is  possible  during  the  early  life  of  many  aquatic  species. 

Branchial  respiration  is,  however,  the  prevalent  type  among  aquatic 
nymphs  and  is  perhaps  the  most  important  of  their  adaptive  character- 
istics. Thin-walled  and  extensive  outgrowths  of  the  integument,  con- 
taining tracheal  branches  or,  rarely,  only  blood  {Blood  gills)  enable 
these  forms  to  obtain  air  from  the  water.  May  fly  nymphs  (Figs.  20, 
A  ;  170),  with  their  ample  waving  gills,  offer  familiar  examples  of  branch- 
ial respiration.  Tracheal  gills  are  very  diverse  in  form  and  situation, 
occurring  in  a  few  species  of  May  fly  nymphs  on  the  thorax  or  head, 


170 


ENTOMOLOGY 


though  commonly  restricted  to  the  sides  of  the  abdomen,  where  they 
occur  in  pairs  or  in  paired  clusters  (Fig.  20,  A).  Caudal  gills  are  found 
in  agrionid  nymphs  (Fig.  173).  The  aquatic  caterpillars  of  Pam^ow;>a 
(Fig.  174)  are  unique  among  Lepidoptera  in  having  gills,  which  are 
filamentous  in  this  instance. 

Caddis  worms,  enclosed  in  their  cases,  maintain  a  current  of  water  by 
means  of  undulatory  movements  of  the  body,  and  the  larvae  and  pupae 
of  most  black-flies  (Simuliidae,  Fig.  233)  secure  a  continuous  supply  of 
fresh  air  simply  by  fastening  themselves  to  rocks  in  swiftly  flowing 
streams. 

Rectal  respiration  is  highly  developed  in  dragon  fly  nymphs.  In 
these,  the  rectum  is  lined  with  thousands  of 
tracheal  branches,  which  are  bathed  by  water 
drawn  in  from  behind,  and  then  expelled. 

All  these  kinds  of  respiration— cutaneous, 
branchial  and  rectal — occur  in  young  ephemerid 
nymphs;  while  mosquito  larvae  have  in  addition 
spiracular  respiration. 

With  the  arrival  of  imaginal  life,  tracheal 
gills  disappear,  except  in  Perlidae,  and  even  in 
these  insects  the  gills  are  of  little,  if  any,  use. 

Marine  Insects. — Except  along  the  shore, 
the  sea  is  almost  devoid  of  insect  life,  the  excep- 
tions being  a  few  chironomid  larvae  which  have 
been  dredged  in  deep  water,  and  fifteen  species 
of  Halohates  (belonging  to  the  same  family  as 
our  famihar  pond-skaters),  which  are  found  on  warm  smooth  seas, 
where  they  subsist  on  floating  animal  remains. 

Between  tide-marks  may  be  found  various  beetles  and  collembolans, 
which  feed  upon  organic  debris;  as  the  tide  rises,  the  former  retreat, 
but  the  latter  commonly  burrow  in  the  sand  or  under  stones  and  become 
submerged,  for  example  the  common  Anurida  maritima. 

Insect  Drift.— Seaweed  or  other  refuse  cast  upon  the  shore  harbors 
a  great  variety  of  insects,  especially  dipterous  larvae,  staphylinid  scaven- 
gers and  predaceous  Carabidae.  On  the  shores  of  inland  ponds  and 
lakes  a  similar  assemblage  of  insects  may  be  found  feeding  for  the  most 
part  on  the  remains  of  plants  or  animals,  or  else  on  one  another.  During 
a  strong  wind,  the  leeward  shore  of  a  lake  is  an  excellent  collecting 
ground,  as  many  insects  are  driven  against  it.  On  the  shores  of  the 
Great  Lakes  insects  are  occasionally  cast  up  in  immense  numbers,  form- 


FlG.  233. — Simulium;. 
A,  larva;  B,  pupa,  show- 
ing respiratory  filaments. 


ADAPTATIONS    OF    AQUATIC    INSECTS  17I 

ing  a  broad  windrow,  fifty  or  perhaps  a  hundred  miles  long.  Needham 
has  described  such  an  occurrence  on  the  west  shore  of  Lake  Michigan, 
following  a  gale  from  the  northeast.  In  this  instance,  a  liter  of  the 
drift  contained  nearly  four  thousand  insects,  of  which  66  per  cent,  were 
crickets  (Nemobius),  20  per  cent.  Locustidae,  and  the  remainder  mostly 
beetles  (Carabidae,  Scarabaeidae,  Chrysomelidae,  Coccinellidae,  etc.), 
dragon  flies,  moths,  butterflies  {Anosia,  Pieris,  etc.)  and  various 
Hemiptera,  Hymenoptera  and  Diptera.  A  large  proportion  of  the  insects 
were  aquatic  forms,  such  as  Hydrophilus,  Cybister,  Zaitha,  and  a  species 
of  caddis  fly;  these  had  doubtless  been  carried  out  by  freshets,  while  the 
butterflies  and  dragon  flies  had  been  borne  out  by  a  strong  wind  from 
the  northwest,  after  which  all  were  driven  back  to  the  coast  by  a  north- 
east wind.  While  some  of  these  insects  survived,  notably  Coccinellidae, 
Trichoptera,  Asilidae,  Locustidae  and  Gryllidae,  nearly  all  the  rest  were 
dead  or  dying,  including  the  dragon  flies,  flies,  bumblebees  and  wasps. 
Foraging  Carabidae  were  observed  in  large  numbers,  also  scavengers  of 
the  families  Staphylinidae,  Silphidae  and  Dermestidae. 

On  the  seashore  and  on  the  shores  of  the  Great  Lakes,  the  salient 
features  of  insect  life  are  essentially  the  same.  Similar  species  occur  in 
the  two  places  with  similar  biological  relations,  on  account  of  the  general 
similarity  of  environment. 

Origin  of  the  Aquatic  Habit. — The  theory  that  terrestrial  insects 
have  arisen  from  aquatic  species  is  no  longer  tenable,  for  the  evidence 
shows  that  the  terrestrial  type  is  the  more  primitive.  Aquatic  insects 
still  retain  the  terrestrial  type  of  organization,  which  remains  unob- 
scured  by  the  temporary  and  comparatively  slight  adaptations  for  an 
aquatic  life.  Thus,  the  development  of  tracheal  gills  has  involved  no 
important  modification  of  the  fundamental  plan  of  tracheal  respiration. 
It  is  significant,  moreover,  that  the  most  generalized,  or  most  primitive, 
insects — Thysanura — are  without  exception  terrestrial.  Aquatic  in- 
sects do  not  constitute  a  phylogenetic  unit,  but  represent  various  orders, 
which  are  for  the  most  part  undoubtedly  terrestrial,  notwithstanding  the 
fact  that  a  few  of  these  orders  (Plecoptera,  Ephemerida,  Odonata,  Tri- 
choptera) are  now  wholly  aquatic  in  habit.  Adaptations  for  an  aquatic 
existence  have  arisen  independently  and  often,  in  the  most  diverse 
orders  of  insects. 


CHAPTER  V 

COLOR  AND  COLORATION 

The  naturalist  distinguishes  between  the  terms  color  and  coloration. 
A  color  is  a  single  hue,  while  coloration  refers  to  the  arrangement  of  colors. 

Sources  of  Color. — The  colors  of  insects  are  classed  as  (i)  pigmental 
{chemical).,  those  due  to  internal  pigments;  (2)  structural  {physical), 
those  due  to  structures  that  cause  interference  or  reflection  of  light; 
and  (3)  combination  colors  {chemico-physical) ,  which  are  produced  in 
both  ways  at  once. 

Structural  Colors. — The  iridescence  of  a  fly's  wing  and  that  of  a 
soap  bubble  are  produced  in  essentially  the  same  way.  The  wing,  how- 
ever, consists  of  two  thin,  transparent,  slightly  separated  lamellae,  which 
diffract  white  light  into  prismatic  rays,  the  color  differences  depending 
upon  differences  in  the  distance  between  the  two  membranes. 

The  brilliant  iridescent  hues  of  many  butterfly  scales  are  due  to  the 
diffraction  of  light  by  fine,  closely  parallel  striae  (Fig.  95)  just  as  in  the 
case  of  the  "dift'raction  gratings"  used  by  the  physicist,  which  consist  of 
a  glass  or  metalHc  plate  with  parallel  equidistant  diamond  rulings  of 
microscopic  fineness.  The  particular  color  produced  depends  in  both 
cases  upon  the  distance  between  the  striae.  Though  almost  all  lepidop- 
terous  scales  are  striated,  it  is  only  now  and  then  that  the  striae  are 
sufficiently  close  together  to  give  diffraction  colors.  In  a  Brazilian 
species  of  Apatura  the  iridescent  scales  have  1,050  striae  to  themilhmeter, 
and  in  a  species  of  Morpho,  according  to  Kellogg,  the  iridescent  pig- 
mented scales  have  1,400  striae  per  millimeter,  the  striae  being  only 
.0007  mm.  apart;  while  in  some  of  the  finest  Rowland  gratings  they 
number  about  1,200  per  millimeter. 

In  the  well  known  diamond  beetle  the  green  dots  of  the  elytra  are 
depressions  from  which  spring  brilliant  and  exquisitely  colored  scales, 
the  colors  varying  throughout  the  range  of  the  spectrum;  green,  however, 
predominating.  These  colors  are  due  to  diffraction  from  regular  stria- 
tions,  with  a  "grating"  space  of  a  thousandth  to  a  two-thousandth  of  a 
millimeter.  On  immersing  the  specimen  in  oil  or  other  liquid  little  or 
no  change  is  observed,  except  in  those  specimens  in  which  a  small 
communicating  aperture  exists  in  the  neck  of  the  scale.     The  oil  can  be 

172 


COLOR   AND    COLORATION  1 73 

seen  gradually  to  till  the  interior,  and  simultaneously  all  trace  of  color 
vanishes  (except  sometimes  a  faint  greenish  surface  color).  It  appears, 
then,  that  the  color  in  this  case  is  due  to  fine  striations  on  the  interior 
surface  of  the  scale.     (Michelson.) 

The  interference  coIofs  of  butterfly  scales  may  be  due,  not  only  to 
surface  markings,  but  also  to  the  lamination  of  the  scale  and  to  the 
overlapping  of  two  or  more  scales.  In  beetles  the  brilliant  blues  and 
greens,  and  iridescence  in  general,  are  sometimes  produced  by  minute 
lines  or  pits  that  diffract  the  light.  According  to  Tower,  "The  pits 
alone,  however,  are  powerless  to  produce  any  color;  it  is  only  when  they 
are  combined  with  a  highly  reflecting  and  refractive  surface  lamella  and 
a  pigmented  layer  below  that  the  iridescent  color  appears.  The  action 
of  light  is  in  this  case  the  same  as  in  the  plain  metaUic  coloring,  excepting 
that  each  pit  acts  as  a  revolving  prism  to  disperse  different  wave-lengths 
of  light  in  different  directions,  and  the  combined  result  is  iridescence. 
The  existence  of  minute  pits  over  the  body  surface  is  of  common  occur- 
rence, but  it  is  only  when  they  are  combined  as  above  that  iridescent 
colors  occur." 

The  production  of  color  by  "metallic"  reflection  deserves  more 
attention  than  it  has  received  from  naturalists.  The  metallic  colors 
of  birds  and  insects  have  been  studied  precisely  by  Professor  Michelson, 
who  has  proved  that  they  are  due  to  the  same  causes  in  both  animals 
and  metals.  The  metals,  on  account  of  their  extraordinary  opacity, 
throw  back  practically  all  the  light  that  strikes  them,  thus  giving  the 
characteristic  brilliant  reflections;  the  distance  to  which  light  can  pen- 
etrate in  most  metals  being  only  a  small  fraction  of  a  light  wave,  so 
that  a  wave-motion  such  as  constitutes  light,  strictly  speaking,  can 
not  be  propagated  at  all.  As  this  opacity  may  be  different  for  different 
colors,  some  would  be  transmitted  more  freely  than  others,  so  that  the 
resulting  transmitted  light  would  be  colored;  and  the  reflected  Ught 
would  be  approximately  complementary  to  the  transmitted  color. 
(Michelson.)  Thus  the  reflected  light  from  the  metal  gold  is  yeUow, 
the  transmitted  light  being  blue.  In  certain  pigeons,  peacocks,  hum- 
ming birds,  as  well  as  a  number  of  butterflies,  beetles  and  other  insects, 
the  brilliant  metaUic  colors  are  due  to  an  extremely  thin  surface  film 
which  has  optical  qualities  like  those  of  metals.  This  film  in  the  case 
of  the  coppery  wing  cover  of  a  beetle  was  calculated  by  Micheson  to  be 
less  than  a  ten-thousandth  of  a  milHmeter  in  thickness. 

In  animals,  as  in  metals,  these  colors  are  brilliant  because  a  large 
percentage  of  the  incident  light  is  reflected.     The  color  of  the  reflected 


174  ENTOMOLOGY 

light  is  complementary  to  that  of  the  transmitted.  Furthermore,  the 
color  of  the  reflected  light  changes  when  the  surface  is  inclined,  the  color 
always  approaching  the  violet  end  of  the  spectrum  as  the  incidence 
increases.  "If  the  color  of  the  normal  reflection  is  violet  the  Hght 
vanishes  (changing  to  ultra-violet),  and  if -the  normal  radiation  be 
infra-red  it  passes  through  red,  orange,  and  yellow  as  the  incidence 
increases."     (Michelson.) 

Professor  Michelson  states  that  the  metallic  and  spectrum  colors 
of  the  tiger  beetles,  CicindelidcB,  are  chiefly  if  not  entirely  true  surface 
or  metalHc  colors,  produced  by  a  film  of  ultra-microscopic  thickness, 
probably  less  than  a  ten-thousandth  of  a  millimeter.  This  film  must 
be  lacking  in  the  dead  black  variety  of  Cicindela  scutellaris,  which  is 
without  trace  of  color,  hke  a  piece  of  black  paper,  Michelson  is 
inclined  to  attribute  differences  in  the  colors  to  differences  in  the  chemi- 
cal constitution  of  the  film,  and  color  changes  during  ontogeny  to 
changes  in  chemical  constitution,  but  states  that  this  would  be  very 
difficult  to  demonstrate  on  account  of  the  minuteness  of  the  film. 
(Shelford.) 

Silvery  white  effects  are  usually  caused  by  the  total  reflection  of 
light  from  scales  or  other  sacs  that  are  filled  with  air;  the  same  silvery 
appearance  is  given  also  by  air-filled  tracheae  and  by  the  air  bubbles 
that  many  aquatic  insects  carry  about  under  water. 

Violet,  blue-green,  coppery,  silver  and  gold  colors  are,  with  few 
exceptions,  structural  colors.     (Mayer.) 

Pigmental  Colors. — These  are  either  cuticular  or  hypodermal.  The 
predominant  brown  and  black  colors  of  insects  are  made  by  pigment 
diffused  in  the  outer  layer  of  the  cuticula  (Fig.  90).  Cockroaches  are 
almost  white  just  after  a  molt,  but  soon  become  brown,  and  many 
beetles  change  gradually  from  brown  to  black.  In  these  cases  it  is 
apparently  significant  that  the  cuticular  pigments  lie  close  to  the  surface 
of  the  skin,  i.  e.,  where  they  are  most  exposed  to  atmospheric  influences. 
Gortner  found  that  the  black  cuticular  pigment  in  the  Colorado  potato 
beetle  {Leptinotarsa)  and  the  brown  or  black .  pigments  of  the  tiger 
beetles  (Cicindela)  belong  to  the  group  of  melanins  and  are  produced  by 
oxidation,  induced  by  an  oxidase;  that  when  all  oxygen  is  absent  no 
pigmentation  takes  place. 

The  cuticular  pigments  are  derived,  of  course,  from  the  underlying 
hypodermis  cells,  and  these  cells  themselves,  moreover,  usually  contain 
(i)  colored  granules  or  fatty  drops  which  give  red,  yellow,  orange  and 
sometimes  white  or  gold  colors  as  seen  through  the  skin;  (2)  diffused 


COLOR   AND    COLORATION  1 75 

chlorophyll  (green)  or  xanthophyll  (yellow),  taken  from  the  food  plant. 
Unlike  the  structural  colors,  which  are  persistent,  these  hypodermal 
colors  often  change  after  death,  though  less  rapidly  when  the  pigments 
are  tightly  enclosed,  as  in  scales  or  hairs.  Though  white  and  green  are 
structural  colors  as  a  rule,  they  are  due  to  pigments  in  Pieridag,  Lycaeni- 
dae  and  some  Geometridae. 

Frequently  a  color  pattern  consists  partly  of  cuticular  and  partly  of 
hypodermal  colors,  the  hypodermal  or  sub-hypodermal  color  forming  "a 
groundwork  upon  which  the  pattern  is  cut  out  by  the  cuticular  color." 
(Tower.)  Thus  in  the  Colorado  potato  beetle,  Leptinotarsa  decemlineata, 
the  pattern  ''is  composed  of  a  dark  cuticular  pigment  upon  a  yellow 
hypodermal  background." 

The  pigment  present  in  the  cuticula  of  tiger  beetles  is  essentially  all 
in  the  primary  cuticula,  and  is  always  either  brown  or  black.  In 
certain  areas  the  primary  cuticula  is  pigmented  and  in  certain  areas 
clear  and  transparent.  This  gives  the  color  pattern.  The  secondary 
cuticula  beneath  the  unpigmented  areas  is  full  of  pore  canals  and  large 
air-filled  interlamellar  spaces,  and  these  give  the  efifect  of  a  white  or 
straw  color  depending  upon  the  color  of  the  secondary  cuticula  itself. 
(Shelford.) 

Combination  Colors. — The  splendid  changeable  hues  of  Apatura, 
Euplcea  and  other  tropical  butterflies  depend  upon  the  fact  that  their 
scales  are  both  pigmented  and  striated.  Under  the  microscope,  certain 
Apatura  scales  are  brown  by  transmitted  light  and  violet  by  reflected 
light,  and  to  the  unaided  eye  the  color  of  the  wing  is  either  brown  or 
violet,  according  as  the  light  is  received  respectively  from  the  pigment 
or  from  the  striated  surfaces  of  the  scales. 

Nature  of  Pigments. — Some  pigments  are  taken  bodily  from  the 
food;  others  are  manufactured  indirectly  from  the  food,  and  some  of 
these  are  excretory  products. 

The  green  color  of  many  caterpillars  and  grasshoppers  is  due  to 
chlorophyll,  which  tinges  the  blood  and  shows  through  the  transparent 
integument.  Mayer  has  found  that  scales  of  Lepidoptera  contain  only 
blood  while  the  pigment  is  forming;  that  the  first  color  to  appear  upon 
the  pupal  wings  is  a  dull  ochre  or  drab — the  same  color  that  the  blood 
assumes  when  it  is  removed  from  the  pupa  and  exposed  to  the  air ;  also 
that  pigments  like  those  of  the  wings  may  be  manufactured  artificially 
from  pupal  blood.  Pieridae  are  peculiar  in  thenature  of  their  pigments, 
as  Hopkins  has  shown.  The  white  pigment  of  this  family  is  uric  acid 
and  the  reds  and  yellows  of  Pieris,  Colias  and  Papilio  are  due  to  deriva-  . 


176  ENTOMOLOGY 

tives  of  uric  acid;  the  yellow  pigment,  termed  lepidotic  acid,  precedes 
the  red  in  time  of  appearance,  the  latter  being  probably  a  derivative 
of  the  former.  The  green  pigments  of  some  Papilionidae,  Noctuidse, 
Geometridae  and  Sphingidae  are  also  said  by  some  investigators  to  be 
products  of  uric  acid,  which  in  insects  as  in  other  animals  is  primarily 
an  excretory,  or  waste,  product. 

Effects  of  Food  on  Color. — Besides  chlorophyll,  to  which  various 
caterpillars,  aphids  and  other  forms  owe  their  green  color,  the  yellow 
constituent  of  chlorophyll,  namely  xanthophyll,  frequently  imparts  its 
color  to  plant-eating  insects,  while  some  phytophagous  species  are  dull 
yellow  or  brown  from  the  presence  of  tannin,  taken  from  the  food  plant. 
Most  pigments,  however,  are  elaborated  from  the  food  by  chemical 
processes  that  are  not  well  understood. 

Many  who  have  reared  Lepidoptera  extensively  know  that  the  color 
of  the  imago  is  influenced  by  the  character  of  the  larval  food,  other  con- 
ditions being  equal,  and  are  able  at  will  to  effect  certain  color  changes 
simply  by  feeding  the  larvae  from  birth  upon  particular  kinds  of  plants. 
In  this  country  we  have  few  observations  upon  the  subject,  but  in  Europe 
the  effects  of  food  upon  coloration  have  been  ascertained  in  the  case  of 
many  species  of  Lepidoptera.  According  to  Gregson,  Hybernia  defolia- 
ria  is  richly  colored  when  fed  upon  birch,  but  is  dull  colored  and  almost 
unmarked  when  fed  on  elm.  Pictet,  by  feeding  larvae  of  Vanessa 
urticxB  on  the  flowers  instead  of  the  leaves  of  the  nettle  obtained  the 
variety  known  as  urticoides.  Food  affects  the  color  of  the  larva  also, 
as  Poulton  found  in  the  case  of  caterpillars  of  Tryphcena  pronuba,  all 
from  the  same  batch  of  eggs.  When  fed  with  only  the  white  midribs 
of  cabbage  leaves,  the  larvae  remained  almost  white  for  a  time,  but 
afterward  showed  a  moderate  amount  of  black  pigment;  when  fed  with 
the  yellow  etiolated  heart-leaves  or  the  dark  green  external  leaves, 
however,  the  larvae  all  became  bright  green  or  brown — the  same  pigment 
being  derived  indifferently  from  etiolin  (probably  the  same  substance 
as  xanthophyll)  or  chlorophyll. 

Though  the  pigments  may  differ  in  color  or  amount  according  to 
the  kind  of  food,  the  color  patterns  vary  without  regard  to  food.  Thus 
Callosamia  promethea,  Leptinotarsa  decemlineata  (Colorado  potato 
beetle),  CoccineUidae  (lady-bird  beetles)  and  a  host  of  other  insects 
exhibit  extensive  individual  variations  in  coloration  under  precisely 
the  same  food  conditions.  Caterpillars  of  the  same  kind  and  age  are 
often  very  differently  marked  when  feeding  upon  the  same  plant;  for 
example,  Chloridea  obsoleta  (corn  worm)  and  the  sphingid  Deilephila 


COLOR   AND    COLORATION  1 77 

Uneata.  Furthermore,  striking  changes  of  coloration  accompany  each 
molt  in  most  caterpillars,  but  particularly  those  of  butterflies,  and 
these  changes  may  prove  to  have  an  important  phylogenetic  signifi- 
cance. Individual  differences  of  coloration  apart  from  those  due  to  the 
direct  action  of  food,  light,  temperature  and  other  environmental 
conditions  are  to  be  explained  by  heredity. 

Effects  of  Light  and  Darkness.— Sunlight  is  an  important  factor  in 
the  development  of  most  animal  pigments,  as  they  will  not  develop  in 
its  absence.  The  collembolan  Anurida  maritima  is  white  at  hatching, 
but  soon  becomes  indigo  blue,  unless  shielded  from  sunhght,  in  which 
event  it  remains  white  until  exposed  to  the  sunhght,  when  it  assumes  the 
blue  color.  Subterranean  or  wood-boring  larvae  are  commonly  white 
or  yellow,  but  never  highly  colored.  The  most  notable  instances, 
however,  are  furnished  by  cave  insects.  These,  like  other  cavernico- 
lous  animals,  are  characteristically  white  or  pale  from  the  absence  of 
pigment,  if  they  live  in  regions  of  continual  darkness,  but  have  more  or 
less  pigmentation  in  proportion  respectively  to  the  greater  or  less 
amount  of  sunlight  to  which  they  have  access. 

Curiously  enough,  light  often  hastens  the  destruction  of  pigment  in 
insects  that  are  no  longer  alive,  for  which  reason  it  is  necessary  to  keep 
cabinet  specimens  in  the  dark  as  much  as  possible.  Life  is  evidently  es- 
sential for  the  sustention  or  renewal  of  the  pigments. 

A  chrysalis  not  infrequently  matches  its  surroundings  in  color.  This 
phenomenon  has  been  investigated  by  Poulton,  who  has  proved  that  the 
color  of  the  chrysalis  is  determined  largely  by  the  prevalent  color  of 
the  surroundings  during  the  last  few  days  of  larval  life.  Larvae  of  the 
cabbage  butterfly,  Pieris  rapcB,  raised  upon  the  same  food  plant  (all 
other  conditions  being  made  as  nearly  equal  as  possible)  produced  dark 
pupae  if  kept  in  darkness  for  a  few  days  just  before  pupation;  yellow 
light  arrested  the  formation  of  the  dark  pigment  and  gave  green  pupae; 
while  light  colors  in  general  gave  light-colored  pupae.  This  color 
resemblance  is  commonly  assumed  to  be  of  protective  value,  and  per- 
haps it  is.  Nevertheless,  it  is  a  direct  effect  of  light,  and  does  not  need 
to  be  explained  by  natural  selection,  even  though  it  cannot  be  denied 
that  natural  selection  may  have  helped  in  its  production. 

Poulton  extended  his  studies  to  the  adaptive  coloration  of  caterpillars 
and  has  published  the  results  of  an  extensive  series  of  experiments  which 
prove  that  the  colors  of  certain  caterpillars  also  are  directly  produced  by 
the  same  colors  in  the  surrounding  light.  Gastropacha  quercifolia,  which 
always  rests  by  day  on  the  older  wood  of  its  food  plant,  was  given  black 


1 78  ENTOMOLOGY 

twigs,  reddish  brown  sticks,  lichens,  etc.,  to  rest  upon,  and  though  all  the 
larvae  were  from  the  same  cluster  of  eggs,  and  had  been  fed  in  the  same 
way,  each  larva  gradually  assumed  the  color  or  colors  of  its  resting  place, 
resulting  in  exquisite  examples  of  protective  resemblance,  the  most  re- 
markable of  which  were  those  in  which  the  larvae  assumed  the  variegated 
coloration  of  lichens.  Only  the  younger  larvae,  however,  proved  to  be 
susceptible  to  the  colors  of  the  environment;  unlike  those  of  Amphidasis 
hetidaria,  in  which  the  older  larvae  also  were  sensitive  to  the  surrounding 
light.  Here  again,  natural  selection  is  unnecessary,  even  if  not  super- 
fluous, as  an  explanation  of  this  kind  of  protective  coloration. 

Professor  W.  M.  Wheeler  has  suggested  that  "such  phenomena  as 
the  permanent  protective  coloration  of  insects  may  be  regarded  as  the 
stereotyped,  highly  specialized  end-stage  of  a  more  ancient  ability 
actively  to  change  color  in  response  to  color  changes  in  the  environment, 
an  abiHty  still  possessed  by  some  primitive  insects  like  the  grasshoppers 
and  mantids,  though  much  more  pronounced  in  cephalopod  mollusks, 
fishes,  amphibia  and  Hzards." 

Effects  of  Temperature. — The  amount  of  a  pigment  in  the  wing  of  a 
butterfly  depends  in  great  measure  upon  the  surrounding  temperature 
during  the  pupal  stage,  when  the  pigments  are  forming.  Black  or  brown 
spots  have  been  enlarged  artificially  by  subjecting  chrysalides  to  cold; 
hence  it  is  probable  that  the  characteristically  large  black  spots  on  the 
under  side  of  the  wings  of  the  spring  brood  of  our  Cyaniris  pseudargiolus 
are  simply  a  direct  effect  of  cold  upon  the  wintering  chrysalides. 
Similarly  the  spring  brood  (variety  marcia)  of  Phyciodes  tharos  owes  its 
distinctive  coloration  to  cold,  as  Edwards  has  proved  experimentally. 
Lepidoptera  have  been  the  subject  of  very  many  temperature  experi- 
ments, some  of  which  will  be  mentioned  presently  in  the  consideration 
of  seasonal  coloration. 

Speaking  generally,  warmth  (except  in  melanism)  tends  to  induce  a 
brightening  and  cold  a  darkening  of  coloration,  the  darkening 
being  due  to  an  increased  amount  of  black  or  brown  pigment.  Temper- 
ature, whether  high  or  low,  seldom  if  ever  produces  new  pigments, 
but  simply  alters  the  amount  and  distribution  of  pigments  that  are 
present  already. 

Effects  of  Moisture. — Very  Httle  is  known  as  to  the  effects  of  mois- 
ture upon  coloration.  The  dark  colors  of  insular  or  coastal  insects  as 
contrasted  with  inland  forms,  and  the  predominance  of  dull  or  suffused 
species  in  mountainous  regions  of  high  humidity,  have  led  observers 
occasionally  to  ascribe  melanism  and  sufusion  to  humidity.     In  these 


COLOR   AND    COLORATION  1 79 

cases,  however,  the  possible  influence  of  low  temperature  and  other 
factors  must  be  taken  into  consideration.  The  experiments  of  Merrifield 
and  of  Standfuss  showed  no  effect  of  moisture  upon  lepidopterous  pupae. 

Pictet  has  found,  however,  that  humidity  acting  on  the  caterpillars 
of  Vatiessa  urtica  and  V.  polychloros  has  a  conspicuous  effect  on  the 
coloration  of  the  butterflies.  Thus  when  the  caterpillars  were  fed  for 
ten  days  with  moist  leaves,  the  resulting  butterflies  had  abnormal 
black  markings  on  the  wings,  and  the  same  results  followed  when  the 
larvas  were  kept  in  an  atmosphere  saturated  with  moisture. 

Climatal  Coloration. — The  brilliant  and  varied  colors  of  tropical 
insects  are  popularly  ascribed  to  intense  heat,  light  and  moisture;  and 
the  dull  monotonous  colors  of  arctic  insects,  similarly  to  the  surrounding 
climatal  conditions  Climate  undoubtedly  exerts  a  strong  influence 
upon  coloration,  but  the  precise  nature  of  this  influence  is  obscure  and  will 
remain  so  until  more  is  known  about  the  effects  separately  produced  by 
each  of  the  several  factors  that  go  to  make  up  what  is  called  cHmate. 

The  prevalence  of  intense  and  varied  colors  among  tropical  insects 
is  doubtless  somewhat  exaggerated,  for  the  reason  that  the  highly 
colored  species  naturally  attract  the  eye  to  the  exclusion  of  the  less 
conspicuous  forms.  Indeed,  Wallace  assures  us  that,  although  tropi- 
cal insects  present  some  of  the  most  gorgeous  colors  in  the  whole  realm 
of  nature,  there  are  thousands  of  tropical  species  that  are  as  dull  colored 
as  any  of  the  temperate  regions.  Carabidae,  in  fact,  attain  their  greatest 
brilliancy  in  the  temperate  zone,  according  to  Wallace,  though  butter- 
flies certainly  show  a  larger  proportion  of  vivid  and  varied  colors  in  the 
tropics.  Mayer  finds,  in  the  widely  distributed  genus  Papilio,  that  200 
South  American  species  display  but  36  colors,  while  22  North  American 
species  show  17.  While  the  number  of  species  in  South  America  is 
nine  times  as  great  as  in  North  America,  the  number  of  colors  displayed 
is  only  a  little  more  than  twice  as  great;  hence  Mayer  concludes  that 
the  richer  display  of  colors  in  the  tropics  may  be  due  to  the  far  greater 
number  of  species,  which  gives  a  better  opportunity  for  color  sports  to 
arise;  and  not  to  any  direct  influence  of  the  climate.  Furthermore,  the 
number  of  broods  which  occur  in  a  year  is  much  greater  in  the  tropics 
than  in  the  temperate  zones,  so  that  the  tropical  species  must  possess  a 
correspondingly  greater  opportunity  to  vary. 

Albinism  and  Melanism. — These  interesting  phenomena,  wide- 
spread among  the  higher  animals,  have  often  been  attributed  to  tempera- 
ture, but  albinism  and  melanism  are,  in  some  instances  at  least, 
strongly  inherited  without  regard  to  temperature. 


l8o  ENTOMOLOGY 

Albinism  is  exceptional  whiteness  or  paleness  of  coloration,  and  is 
due  usually  to  deficiency  of  pigment,  but  in  some  instances  (Pieridae) 
to  the  presence  of  a  white  pigment. 

The  common  yellow  butterfly,  Colias  philodice,  and  its  relatives, 
are  frequently  albinic.  Scudder  observed  that  albinism  among  butter- 
flies in  America  appears  to  be  confined  to  a  few  Pieridae,  and  to  be  re- 
stricted to  the  female  sex;  is  more  common  in  subarctic  and  subalpine 
regions  than  in  lower  latitudes  and  altitudes,  and  only  in  the  former 
places  includes  all  the  females.  At  low  altitudes,  however,  instead  of  ap- 
pearing early  in  the  year  as  might  be  expected,  the  albinic  forms  appear 
during  the  warmer  months. 

The  experiments  made  by  Gerould  on  C.  philodice  show  that  the 
number  of  albinic  female  offspring  from  white  females  crossed  with 
yellow  males  is  in  accordance  with  Mendelian  law.  Albinism  is  not 
entirely  confined  to  the  female  as  Scudder  thought,  for  white  males 
occur,  though  they  are  extremely  rare.  ''They  may  be  expected  in 
regions  where  the  white  female  is  especially  abundant"  (Gerould). 

In  Europe  there  are  many  albinic  species  of  butterflies,  and  they 
are  by  no  means  confined  to  family  Pieridae. 

Melanism  is  unusual  blackness  or  darkness  of  coloration.  As  to 
how  it  is  produced  little  is  known,  though  warmth  is  probably  the  most 
potent  influence,  and  some  attribute  it  to  moisture,  as  was  mentioned. 
Pictet  obtained  partial  melanism  in  Vanessa  urticce  and  V.  polychloros 
by  subjecting  the  larvae  to  moisture. 

In  warm  latitudes,  some  females  of  our  Papilio  glaucus  are  blackish 
brown  with  black  markings,  instead  of  being,  as  usual,  yellow  with 
black  markings.  In  the  South,  some  males  of  the  spring  brood  of 
Cyaniris  pseudargiolus  are  partly  or  wholly  brown  instead  of  blue. 
A  melanic  male  of  Colias  philodice  occurs  as  an  extremely  rare  muta- 
tion. A  melanic  variety  of  pomace  fly,  Drosophila,  with  a  black  body, 
follows  the  Mendelian  law  in  its  appearance  in  breeding  experiments. 

Seasonal  Coloration. — When  butterflies  have  more  than  one  brood 
in  a  year,  the  broods  usually  differ  in  aspect,  sometimes  so  much  that 
their  specific  identity  is  revealed  only  by  rearing  one  brood  from 
another.  The  same  species  may  exist  under  two  or  more  distinct 
forms  during  the  same  season — in  other  words,  may  be  seasonally  dimor- 
phic, trimorphic  or  polymorphic. 

Thus  Polygonia  interrogationis  has  two  forms,  fabricii  and  umhrosa. 
which  differ  not  only  in  coloration,  but  even  in  the  form  of  the  wings 


COLOR    AND    COLORATION 


;8] 


and  the  genitalia.     In  New  England  fahricii  hibernates  and  produces 
umbrosa.  as  a  rule,  while  umhrosa  usually  yields  fahricii. 

The  little,  blue  butterfly,  Cyaniris  pseudargiolus  (Fig.  234),  is  poly- 
morphic to  a  remarkable  degree.     In  the  high  latitudes  of  Canada  a 


Fig.  234. — Cyaniris  pseudargiolus; 


A,  form  lucia;  B,   violacea;   C,   pseudargiolus  proper. 
Natural  size. 


single  brood  {lucia)  occurs.  About  Boston  the  same  spring  brood  ap- 
pears, but  under  two  forms:  an  earlier  variety  {lucia),  which  is  small, 
with  large  black  markings  beneath;  and  a  later  variety  (violacea), 
which  is  typically  larger,  with  smaller  black  spots,  though  it  varies 
into  the  form  lucia.  Finally, 
in  summer,  a  third  form 
{pseudargiolus  proper) 
appears,  as  the  product  of 
lucia  or  else  the  joint  prod- 
uct of  lucia  and  violacea,  and 
this  is  still  larger,  but  the 
black  spots  are  now  faint. 
In  the  warm  South  the  spring 
form  is  violacea,  but  while 
some  of  the  males  are  blue, 
others  are  melanic,  as  just 
mentioned — a  dimorphic  con- 
dition which  does  not  occur 
in  the  North.  Violacea  then 
produces  pseudargiolus,  in 
which,  however,  all  the  males  are  blue. 

'  Iphiclides  ajax  (Fig.  235)  is  another  polymorphic  butterfly  whose 
life  history  is  complex.  The  three  principal  varieties  of  this  species, 
known  respectively  as  marcellus,  telamonides  and  ajax,  differ  not  only  in 
coloration,  but  also  in  size  and  form;  marcellus  appears  first,  in  spring; 
telamonides  appears  a  little  later  (though  before  marcellus  has  disap- 
peared); and  ajax  is  the  summer  form;  as  the  season  advances  the 


Pig.   235. — Iphiclides  ajax,    form    telamonides,  on 
flower  of  button  bush.     Reduced. 


l82 


ENTOMOLOGY 


varieties  become  successively  larger,  with  longer  tails  to  the  hind 
wings. 

Now  Edwards  submitted  chrysalides  of  the  summer  form  ajax  to 
cold  and  thereby  obtained,  in  the  same  summer,  butterflies  with  the 
form  of  ajax  but  the  markings  of  the  spring  form  telamonides .  Some  of 
the  chrysalides,  however,  lasted  over  until  the  next  spring  and  then  gave 
telamonides. 

In  Phyciodes  tharos  (Fig.  236)  the  spring  and  summer  broods,  termed 
respectively  marcia  and  morpheus,  were  at  first  regarded  as  distinct 
species.  In  marcia  the  hind  wings  are  heavily  and  diffusely  marked 
beneath  with  strongly  contrasting  colors,  while  in  morpheus  they  are 
plain  and  but  faintly  marked.  Edwards  placed  upon  ice  eighteen 
chrysalides  that  normally  would  have  produced  morpheus;  but  instead 


Fig.   236. — Phyciodes  tharos;  A,  spring  form,  marcia;  B,  summer  form,  morpheus;  under 
surfaces.      Natural  size. 


of  this,  the  fifteen  imagines  that  emerged  were  all  of  the  spring  form 
marcia  and  were  smaller  than  usual.  Pupae  derived  from  eggs  of  marcia 
gave,  after  artificial  cooling,  not  morpheus ,  but  marcia  again.  The 
evident  conclusion  is  that  the  distinctive  coloration  of  the  spring  variety 
is  brought  about  by  low  temperature.  In  Labrador,  only  one  brood 
occurs — marcia;  in  New  York,  the  species  if  digoneutic  (two-brooded) 
and  in  West  Virginia  polygoneuiic  (several-brooded) . 

Extensive  temperature  experiments  upon  seasonal  dimorphism  in 
Lepidoptera  have  been  conducted  in  Europe  by  some  of  the  most  com- 
petent biologists.  Weismann  found  that  pupse  of  the  summer  form  of 
Pieris  napi,  if  placd  on  ice,  disclosed  the  darker  winter  form,  usually 
in  the  same  season,  though  sometimes  not  until  the  next  spring.  It  was 
found  impossible,  however,  to  change  the  winter  variety  into  the  sum- 
mer one  by  the  application  of  heat.  Similar  results  have  attended  the 
important  and  much-discussed  experiments  of  Dorfmeister,  Weismann 
and  others  upon  Vanessa  levana-prorsa  and  other  species,  from  which  it 
has  been  inferred  by  Weismann  that  the  winter  form  is  the  primary. 


COLOR   AND    COLORATION  1 83 

older,  and  more  stable  of  the  two  forms,  and  the  summer  form  a  second- 
ary, newer,  and  less  stable  variety;  since  the  latter  form  only,  as  a  rule, 
responds  much  to  thermal  influences.  Weismann  argued  that,  in  addi- 
tion to  the  direct  effect  of  temperature,  alternative  inheritance  also 
plays  an  important  part  in  the  production  of  seasonal  varieties.  He 
tried  to  show,  moreover,  that  each  seasonal  variety  is  colored  in  adapta- 
tion to  its  particular  environment  and  that  this  adaptation  may  have 
been  brought  about  by  natural  selection — though  he  did  not  succeed 
in  this  respect. 

In  several  instances,  local  varieties  have  been  artificially  produced 
as  results  of  temperature  control.  Thus  Standfuss  produced  in  Ger- 
many, by  the  application  of  cold,  individuals  of  Vanessa  urticcB  which 
were  indistinguishable  from  the  northern  variety  polaris;  and  from 
pupae  of  Vanessa  cardui,  by  warmth,  a  very  pale  form  like  that  found  in 
the  tropics;  and,  by  cold,  a  dark  variety  similar  to  one  found  in  Lapland. 

Shelford,  by  subjecting  a  pupa  of  a  tiger  beetle,  C.  tranqueharica 
{vulgaris)  to  cold  moist  conditions  (mean  temperature,  12°  C;  moist) 
obtained,  in  Chicago,  a  color  variety  hke  one  that  occurs  naturally  in 
the  eastern  mountains. 

In  a  second  instance,  both  pattern  and  color  were  modified  by  hot 
dry  conditions  (mean  temperature,  37°  C;  dry),  and  a  variety  obtained 
such  as  occurs  in  the  western  states. 

In  a  third  experiment,  both  pattern  and  color  were  modified  by  hot 
wet  conditions  (37°  C;  moist),  and  a  variety  produced  like  one  in  the 
moist  southern  states. 

These  investigators  and  others,  notably  Merrifield  and  Fischer,  have 
accumulated  a  considerable  mass  of  experimental  evidence,  the  inter- 
pretation of  which  is  in  many  respects  difficult,  involving  as  it  does,  not 
merely  the  direct  effect  of  temperature  upon  the  organism,  but  also  deep 
questions  of  heredity,  including  reversion,  individual  variation,  and  the 
inheritance  of  acquired  characters. 

The  seasonal  increase  in  size  that  is  noticeable,  as  in  C.  pseudargiolus 
and  /.  ajax,  is  doubtless  an  expression  of  increasing  metabolism  due  to 
increasing  temperature.  Warmth,  as  is  well  known,  stimulates  growth, 
and  cold  has  a  dwarfing  effect.  While  this  is  true  as  a  rule,  there  are 
some  apparent  exceptions,  however.  Thus  Standfuss  found  that  some 
caterpillars  were  so  much  stimulated  by  unusual  warmth  that  they 
pupated  before  they  were  sufficiently  fed,  and  gave,  therefore,  under- 
sized imagines.  A  moderate  degree  of  warmth,  however,  undoubtedly 
hastens  growth. 


1 84 


ENTOMOLOGY 


Sexual  Coloration. — The  sexes  are  often  distinguished  by  colora- 
tional  as  well  as  structural  differences.  Colorational  antigeny  (this 
word  signifying  secondary  sexual  differences  of  whatever  sort)  is  most 
prevalent  among  butterflies,  in  which  it  is  the  extreme  phase  of  that 


IHHI 

It-e^ 

■^  A 

^^^ 

^^^  r't ^aj 

^™-      i?      ^^ 

^^»-    j^^  ^vj:^ 

fS^^^^-^L^Mk 

l^^ff^f^'^-r-^Jm 

W"^-   ~>l^l 

^k^  '^  /p 

hIr*sLj»^L^^H 

lK^w/''^'A 

i^\vv'^-^  ^H 

^Mfjti./'/  /A 

1^'^^    ^^^1 

^^Hh^//  ^^Kk 

^'v-X^^j^l 

Fig.   237. — Pieris  prolodice;  male  (on  the  left)  and  female  (on  the  right).      Natural  size. 


differentiation  of  ornamentation  for  which  Lepidoptera  are  unrivaled. 

The  male  of  Pieris  protodice  (Fig.  237)  has  a  few  brown  spots  on  the 
front  wings;  the  female  is  checkered  with  brown  on  both  wings.  In 
Colias  philodice  (Fig.  238)  and  C.  eurytheme  the  marginal  black  band  of 
the  front  wings  is  sharp  and  uninterrupted 
in  the  male,  but  diffuse  and  interrupted  by 
yellow  spots  in  the  female.  In  the  genus 
Papilio  the  sexes  are  often  distinguished  by 
colorational  differences  and  in  Hesperiidas 
the  males  often  have  an  oblique  black  dash 
across  the  middle  of  each  front  wing.  Callo- 
samia  promethea  (Fig.  239),  the  gipsy  moth 
and  many  other  Lepidoptera  exhibit  colora- 
tional antigeny.  In  not  a  few  Sesiidae  the 
sexes  differ  greatly  in  coloration.  Thus  in 
the  male  of  the  peach  tree  borer  {Aegeria 
exitiosa)  all  the  wings  are  colorless  and 
transparent;  while  in  the  female  the  front 
wings  are  violet  and  opaque  and  the  fourth 
abdominal  segment  is  orange  above.  The 
same  sex  may  present  two  types  of  coloration,  as  in  males  of  Cyaniris 
pseudargiolus  and  females  oi  Papilio  glaucus,  already  mentioned.  Papilio 
merope,  of  South  Africa,  is  remarkable  in  having  three  females,  which  are 
entirely  different  in  coloration  from  one  another  and  from  the  male. 


Fig.  238. — Colias  philodice; 
right  fore  wing  of  male  (above) 
and  of  female  (below).  Nat- 
ural size. 


COLOR   AND    COLORATION 


i8S 


There  is  no  longer  any  doubt,  it  may  be  added,  as  to  the  specific 
identity  of  these  forms. 

Next  to  Lepidoptera,  Odonata  most  frequently  show  colorational 
antigeny.  The  male  of  Calopteryx  maculata  is  velvety  black;  the  female 
smoky,  with  a  white  pterostigmatal  spot.  Among  Coleoptera,  the  male 
of  Hoplia  trifasciata  is  grayish  and  the  female  reddish  brown;  a  few 
more  examples  might  be 
given,  though  sexual  dif- 
ferences in  coloration  are 
comparatively  rare  among 
beetles.  Of  Hymenoptera, 
some  of  the  Tenthredinidae 
exhibit  colorational 
antigeny. 

Among  tropical  butter- 
flies there  are  not  a  few 
instances  in  which  the 
special  coloration  of  the 
female  is  adaptive — har- 
monizing with  the  sur- 
roundings or  else  imitating 
with  remarkable  precision 
the  coloration  of  another 
species  which  is  known 
to  be  immune  from  the 
attacks  of  birds — as  de- 
scribed beyond.  In  this 
way,  as  Wallace  suggests, 
the  egg-laden  females  may 
escape  destruction,  as  they 
sluggishly  seek  the  proper 
plants  upon  which  to  lay 
their  eggs.  Here  would 
be  a  fair  field  for  the  operation  of  natural  selection. 

In  most  insects,  however,  sexual  differences  in  coloration  are  ap- 
parently of  no  protective  value  and  are  usually  so  trivial  and  variable 
as  probably  to  be  of  no  use  for  recognition  purposes.  The  usual  state- 
ment that  these  differences  facilitate  sexual  recognition  is  a  pure  as- 
sumption, in  the  case  of  insects,  and  one  that  is  inadequate  in  spite  of 
its  plausibility,  for  (i)  it  is  extremely  improbable  from  our  present 


Fig.  239. 


Callosamia  promethea.  A,  male,  clinging  to 
cocoon;  B,  female.      Reduced. 


I 86  ENTOMOLOGY 

knowledge  of  insect  vision  that  insects  are  able  to  perceive  colors  except 
in  the  broadest  way,  namely,  as  masses;  (2)  the  great  majority  of  insect 
species  show  no  sexual  differences  in  coloration;  (3)  when  colorational 
antigeny  is  present  it  is  probably  unnecessary,-  to  say  the  least,  for 
sexual  recognition.  Thus,  notwithstanding  the  marked  dissimilarity 
of  coloration  in  the  two  sexes  of  C.  promethea,  the  males,  guided  by  an 
odor,  seek  out  their  mates  even  when  the  wings  of  the  female  have  been 
amputated  and  male  wings  glued  in  their  place,  as  Mayer  found. 

Hence,  when  useless,  colorational  antigeny  cannot  have  been  de- 
veloped by  natural  selection  and  may  be  due  simply  to  the  extended 
action  of  the  same  forces  that  have  produced  variety  of  coloration  in 
general. 

Origin  of  Color  Patterns. — Tower,  who  has  written  an  important 
work  on  the  colors  and  color  patterns  of  Coleoptera,  finds  that  each  of 
the  black  spots  on  the  pronotum  of  the  Colorado  potato  beetle  (Fig.  240) 
"is  developed  in  connection  with  a  muscle,  and  marks  the  point  of  at- 
tachment of  its  fibres  to  the  cuticula."  Thus  the  color  pattern,  in  its 
origin,  is  not  necessarily  useful.  This  point  is  so  important  that  we 
quote  Tower's  conclusions  in  full.  ''The  most  important  and  widely 
disseminated  of  insect  colors  are  those  of  the  cuticula  .  .  .  these 
colors  develop  as  the  cuticula  hardens,  and  appear  first,  as  a  rule,  upon 
sclerites  to  which  muscles  are  attached.  In  one  of  the  earlier  sections  of 
this  paper  I  showed  that  the  pigment  develops  from  before  backward 
and,  approximately,  by  segments,  excepting  that  it  may  appear  upon 
the  head  and  most  posterior  segments  simultaneously. 

"In  ontogeny  color  appears  first,  as  a  rule,  over  the  muscles  which 
become  active  first,  or  upon  certain  sclerites  of  the  body.  These  are 
usually  the  head  muscles,  although  exceptions  are  not  infrequent.  It 
should  be  remembered  that  as  the  color  appears  the  cuticula  hardens, 
and,  considering  that  muscles  must  have  fixed  ends  for  their  action,  it 
seems  that  there  is  a  definite  relation  between  the  development  of  color, 
the  hardening  of  the  cuticula,  and  the  beginning  of  muscular  activity; 
the  last  being  dependent  upon  the  second,  and,  incidentally,  accom- 
panied by  the  first.  As  muscular  activity  spreads  over  the  animal  the 
cuticula  hardens  and  color  appears,  so  that  color  is  nearly,  if  not 
wholly,  segmentally  developed. 

"The  relation  which  exists  between  cuticular  color  and  the  stift'ening 
of  the  cuticula  is  thus  a  physiological  one,  the  cuticula  not  being  able  to 
harden  without  becoming  yellow  or  brown.  What  bearing  has  this 
upon  the  origin  of  color  patterns?     In  the  lower  forms  of  tracheates, 


COLOR   AND    COLORATION  1 87 

such  as  the  Myriapods,  colors  appear  as  segmental  repetitions  of  spots 
or  pigmented  areas  which  mark  either  important  sclerites  or  muscle 
attachments.  On  the  abdomens  of  insects,  where  segmentation  is  best 
observed,  color  appears  as  well-defined,  segmentally  arranged  spots, 
but  on  the  thorax  segmentation  is  obscured  and  lost  upon  the  head.  Of 
what  importance,  then  is  pigmentation?  And  how  did  it  arise?  If  the 
ontogenetic  stages  offer  any  basis  for  phylogenetic  generalization,  we 
may  conclude  that  cuticula  color  originated  in  connection  with  the 
hardening  of  the  integument  of  the  ancestral  tracheates  as  necessary  to 
the  muscular  activity  of  terrestrial  life.  The  primitive  colors  were 
yellows,  browns  and  blacks,  corresponding  well  with  the  surroundings 
in  which  the  first  terrestrial  insects  are  supposed  to  have  lived.  The 
color  pattern  was  a  segmental  one,  showing  repetition  of  the  same  spots 
upon  successive  segments,  as  upon  the  abdomen  of  Coleoptera. 

"So  firmly  have  these  characters  become  ingrained  in  the  tracheate 
series,  and  so  important  is  this  relation  of  the  hardening  of  the  cuticula 
to  the  musculature  and  to  the  formation  of  body  sclerites,  that  even  the 
most  specialized  forms  show  this  primitive  system  of  coloration;  and, 
although  there  may  be  spots  and  markings  which  have  no  connection 
with  it,  still  the  chief  color  areas  are  thus  closely  associated." 

Development  of  Color  Patterns. — Although  the  causes  of  colora- 
tion are,  for  the  most  part,  obscure,  it  is  possible,  nevertheless,  to  point 
out  certain  paths  along  which  coloration  appears  to  have  developed. 
These  paths  have  been  determined  by  the  comparison  of  color  patterns 
in  kindred  groups  of  insects  and  the  study  of  colorational  variations  in 
adults  of  the  same  species.  Butterflies,  moths  and  beetles  have 
naturally  been  preferred  as  subjects  by  most  students. 

The  most  primitive  colors  among  moths  are  uniform  dull  yellows, 
browns  and  drabs — the  same  colors  that  the  pupal  blood  assumes  when 
it  is  dried  in  the  air.  These  simple  colors  prevail  on  the  hind  wings  of 
most  moths  and  on  the  less  exposed  parts  of  the  wings  of  highly  colored 
butterflies.  The  hind  wings  of  moths  are,  as  a  rule,  more  primitively 
colored  than  the  front  ones  because,  as  Scudder  says,  "all  differentiation 
in  coloring  has  been  greatly  retarded  by  their  almost  universal  conceal- 
ment by  day  beneath  the  overlapping  front  wings."  Exceptions  to 
this  statement  are  found  in  Geo'metridas  and  such  other  moths  as  rest 
with  all  the  wings  spread.  "In  such  hind  wings  we  find  that  the  sim- 
plest departure  from  uniformity  consists  in  a  deepening  of  the  tint  next 
the  outer  margin  of  the  wing;  next  we  have  an  intensification  of  the 
deeper  tint  along  a  line  parallel  to  the  margin;  it  is  but  a  step  from  this 


1 88  ENTOMOLOGY 

condition  to  a  distinct  line  or  band  of  dark  color  parallel  to  the  margin. 
Or  the  marginal  shade  may,  in  a  similar  way,  break  up  into  two  or  more 
transverse  and  parallel  submarginal  lines,  a  very  common  style  of 
ornamentation,  especially  in  moths.  Or,  again,  starting  with  the 
submarginal  shade,  this  may  send  shoots  or  tongues  of  dark  color  a 
short  distance  toward  the  base,  giving  a  serrate  inner  border  to  the 
marginal  shade;  when  now  this  breaks  up  into  one,  two,  or  more  lines 
or  narrow  stripes,  these  stripes  become  zigzag,  or  the  inner  ones  may  be 
zigzag,  while  the  outer  ones  are  plain — a  very  common  phenomenon. 

"A  basis  such  as  this  is  .sufficient  to  account  for  all  the  modifications 
of  simple  transverse  markings  which  adorn  the  wings  of  Lepidoptera." 

Briefly,  one  or  more  bands  may  break  up  into  spots  or  bars,  the 
breaks  occurring  either  between  the  veins  or,  more  commonly,  at  the 
veins;  and  in  the  latter  event,  short  bars  or  more  or  less  quadrate  or 
rounded  spots  arise  in  the  interspaces.  From  simple  round  spots  there 
may  develop,  as  Darwin  and  others  have  shown,  many-colored  eye-like 
spots,  or  ocelli. 

Mayer  gives  the  following  laws  of  color  pattern:  "(a)  Any  spot 
found  upon  the  wing  of  a  butterfly  or  moth  tends  to  be  bilaterally  sym- 
metrical, both  as  regards  form  and  color;  and  the  axis  of  symmetry  is  a 
line  passing  through  the  center  of  the  interspace  in  which  the  spot  is 
found,  parallel  to  the  longitudinal  nervures.  (b)  Spots  tend  to  appear 
not  in  one  interspace  only,  but  in  homologous  places  in  a  row  of  adjacent 
interspaces,  (c)  Bands  of  color  are  often  made  by  the  fusion  of  a  row 
of  adjacent  spots,  and,  conversely,  chains  of  spots  are  often  formed  by 
the  breaking  up  of  bands,  (d)  When  in  process  of  disappearance,  bands 
of  color  usually  shrink  away  at  one  end.  (e)  The  ends  of  a  series  of  spots 
are  more  variable  than  the  middle.  (/)  The  position  of  spots  situated 
near  the  outer  edges  of  the  wing  is  largely  controlled  by  the  wing  folds 
or  creases." 

These  results  have  been  arrived  at  chiefly  by  the  study  of  the  varia- 
tions presented  by  color  patterns. 

Variation  in  Coloration. — It  is  safe  to  say  that  no  two  insects  are 
colored  exactly  alike  Some  species,  however,  are  far  more  variable 
than  others.  Catocala  ilia,  for  example,  occurs  under  more  than  fifty 
varieties,  each  of  which  might  be  given  a  distinctive  name,  were  it  not 
for  the  fact  that  these  varieties  run  into  one  another.  One  may  examine 
hundreds  of  potato  beetles  {L.  decemlineata)  without  finding  any  two 
that  have  precisely  the  same  pattern  on  the  pronotum.     The  range  of 


COLOR   AND    COLORATION  1 89 

this  variation  in  this  species  is  partially  indicated  in  Fig.  240,  and  that 
of  Cicindela  in  Fig.  241. 

Individuals  of  Cicindela  vary  in  pattern  in  a  few  definite  directions, 
and  the  patterns  that  characterize  the  various  species  appear  to  be 
tixations  of  individual  variations.  According  to  Dr.  G.  H.  Horn:  (i) 
The  type  of  marking  is  the  same  in  all  our  species.  (2)  Assuming  a  well- 
marked  species,  tranqueharica  {vulgaris,  Fig.  241,  /)  as  a  central  type, 
the  markings  of  other  species  vary  from  that  type,  (a)  by  a  progressive 
spreading  of  the  white,  {b)  by  a  gradual  thinning  or  absorption  of  the 
white,  (c)  by  a  fragmentation  of  the  markings,  {d)  by  linear  supplemen- 
tary extension.  (3)  Many  species  are  practially  invariable  (i.e.,  the 
individual  variations  are  small  in  amount  as  compared  with  those  in 
other  species) .  These  fall  into  two  series :  (a)  those  of  the  normal  type, 
as  tranqueharica,  hirticoUis  and  tenuisignata;  (b)  those  in  which  some 
modification  of  the  type  has  become  permanent,  probably  through 
isolation,  as  marginipennis,  togala  and  lemniscata.  (4)  Those  species 
which  vary  do  so  in  one  direction  only.  New  types  of  pattern,  of 
specific  value,  appear  to  have  arisen  by  the  isolation  and  perpetuation 
of  individual  variations. 

.    Professor  Shelford,  in  his  important  monograph  on  the  colors  of 
these  beetles,  draws  the  following  conclusions,  among  others: 

Longitudinal  stripes  in  which  pigment  usually  occurs  lie  in  the  area 
of  the  chief  tracheal  trunks  of  the  elytron;  there  are  seven  cross  bands  in 
which  pigment  does  not  develop;  the  second  and  third  and  fifth  and 
sixth  of  these  are  often  joined  to  make  one  of  each  pair. 

Pigment  usually  occurs  about  the  bases  of  hairs,  which  usually  lie 
in  the  lines  of  the  tracheae. 

In  ontogeny  the  elytra  show  a  spotted  condition  corresponding  to  the 
system  of  cross  bands  and  longitudinal  stripes.  The  longitudinal 
stripes  are  usually  more  pronounced. 

The  characteristic  markings  of  the  group  are  composed  of  spots  or 
elements  joined  in  the  longitudinal  light  stripe  areas  and  areas  of  cross 
bands,  with  the  loss  of  various  spots  or  elements  which  occur  in  onto- 
geny; joinings  are  sometimes  obHque,  and  when  so  markings  are  some- 
times parallel  with  the  curved  end  of  the  elytron. 

Certain  particular  types  of  markings  made  up  of  a  few  elements  joined 
in  a  particular  way  characterize  the  majority  of  species  of  the  group. 

These  markings  as  derived  from  the  cross  and  longitudinal  bands  are 
angular;  reduction  of  angles,  straightening  and  turning  into  oblique 


I  go  ENTOMOLOGY 

positions  parallel  with  the  end  of  the  elytron  characterize  modifications 
of  markings.  The  response  to  stimuli  (high  temperature)  is  in  the 
same  direction. 

Response  to  other  stimuli  appears  to  be  in  the  direction  of 
concentric  extension  of  the  markings. 

The  color  patterns  and  structure  to  which  they  are  related  constitute 
a  mechanism,  the  directions  of  movement  of  which  are  hmited,  i.e., 
easier  in  some  directions  than  others;  the  color  pattern  plans  break 
when  the  related  structures  do;  hereditary  changes  and  fluctuations 
due  to  stimulation  during  ontogeny  are  in  the  same  direction;  laws 
governing  the  mechanism  are  the  same  throughout. 

Variations  in  general  fall  into  two  classes:  continuous  {individual 
variations)  and  discontinuous  (mutations) .  The  former  are  always  pres- 
ent, are  slight  in  extent  and  intergrade  with  one  another;  they  are 
distributed  symmetrically  about  a  mean  condition.  The  latter  are 
occasional,  of  considerable  extent  and  sharply  separated  from  the 
normal  condition. 

R.  H.  Johnson  published  an  important  statistical  study  on  evo- 
lution in  the  color  pattern  of  the  lady-beetles.  He  found  both  con- 
tinuous and  discontinuous  variations  present;  that  the  color  pattern  is 
capable  of  modification  by  the  environment;  that  some  modifications 
are  hereditary  characters  and  others  not. 

Replacements. — Examples  of  the  replacement  of  one  color  by 
another  are  familiar  to  all  collectors.  The  red  of  Vanessa  atalanta  and 
CoccinelHdae  may  be  replaced  by  yellow.  These  two  colors  in  many 
butterflies  and  beetles  are  due  to  pigments  that  are  closely  related  to 
each  other  chemically.  Thus  in  the  chrysomeHd  Lina  lapponica 
the  beetle  at  emergence  is  pale  but  soon  becomes  yellow  with  black 
markings,  and  after  several  houts,  under  the  influence  of  sunlight,  the 
yellow  changes  to  red ;  the  change  may  be  prevented,  however,  by  keep- 
ing the  beetle  in  the  dark.  After  death,  the  red  fades  back  through 
orange  to  yellow,  especially  as  the  result  of  exposure  to  sunlight. 
Yellow  in  place  of  red,  then,  may  be  attributed  to  an  arrested  develop- 
ment of  pigment  in  the  living  insect  and  to  a  process  of  reduction  in  the 
dead  insect,  metabolism  having  ceased. 

Yellow  and  green  are  similarly  related.  The  stripes  of  Pcecilocapsus 
lineatus  are  yellow  before  they  become  green,  and  after  death  fade  back 
to  yellow.  As  the  green  pigment  in  most,  if  not  all,  phytophagous  in- 
sects is  chlorophyll,  these  color  changes  are  probably  similar  to  those 
that  occur  in  leaves.    Leaves  grown  in  darkness  are  yellow,  from  the 


COLOR   AND    COLORATION 


^  ■•»/•*- 


U' 


12 


m 


16 


•\       s 


Fig.  240. — Colorational  variations  of  the  pronotum  of  the  Colorado  potato  beetle,  Lepti 
notarsa    decemlineata. 


ENTOMOLOGY 


m 


\    fi 


Fig.  241. — Elytral  color  patterns  of  Cicindela.  1—8  illustrate  reduction^of  dark 
area;  9-14,  extension  of  dark  area;  15,  16,  formation  of  longitudinal  vitta;  17,  18,  linear  ex- 
tension of  markings,  i,  C.  tranquebarica;  2,  fortnosa;  3,  formosa;  4,  pamphila;  5,  limhala;  6, 
togata;  7,  gratiosa;  8,  hamala;  9,  tenuisignata;  10,  marginipennis;  11,  carthagena;  12,  sex- 
giUtata;  13,  carthagena;  14,  splendida;  15,  pusilla;  16,  lemniscata;  17,  gabhi;  18,  dorsalis. — 
After  Horn,  from  Entomological  News. 


COLOR   AND    COLORATION  1 93 

presence  of  etiolin,  and  do  not  turn  green  until  they  are  exposed  to  sun- 
light (or  electric  light),  without  which  chlorophyll  does  not  develop; 
and  as  metabolism  ceases,  chlorophyll  disintegrates,  as  in  autumn, 
leaving  its  yellow  constituent,  xanthophyll,  which  is  very  likely  the 
same  substance  as  etiolin. 

Cicindela  sexguttata  and  Calosoma  scrutator  are  often  blue  in  place  of 
green.  These  colors  in  these  beetles  are  structural,  and  their  variations 
are  to  be  attributed  to  slight  differences  in  the  structure  of  the  surface. 

Green  grasshoppers  occasionally  become  pink  toward  the  close  of 
summer.  No  explanation  has  been  offered  for  this  phenomenon,  though 
it  may  be  remarked  that  when  grasshoppers  are  killed  in  hot  water  the 
normal  green  pigment  turns  to  pink. 

These  changes  of  color  are  apparently  of  no  use  to  the  insect,  being 
merely  incidental  effects  of  Hght,  temperature  or  other  inorganic 
influences. 


CHAPTER  VI 


ADAPTIVE  COLORATION 


Protective  Resemblance. — Every  naturalist  knows  of  many  ani- 
mals that  tend  to  escape  detection  by  resembling  their  surroundings. 
This  phenomenon  of  protective  resemblance  is  richly  exemplified  by  in- 
sects, among  which  one  of  the  most  remarkable  cases  is  furnished  by  the 
Kallima  butterflies,  especially  K.  inachis  of  India  and  K.  paralekta  of  the 
Malay  Archipelago.  The  former  species  (Fig  242)  is  conspicuous  when 
on  the  wing;  its  bright  colors,  however,  are  confined  to  the  upper  surfaces 
of  the  wings,  and  when  these  are  folded  together,  as  in  repose,  the  insect 


Fig.  242.- 


-Kallima  inachis;  A,  upper  surface;  B,  with  wings  closed,  showing  resemblance 
to  a  leaf.       X  3-^. 


resembles  to  perfection  one  of  the  dead  leaves  among  which  it  is  accus- 
tomed to  hide.  The  form,  size  and  color  of  the  leaf  are  accurately  re- 
produced, the  petiole  being  simulated  by  the  tails  of  the  wings.  Two 
parallel  shades,  one  light  and  one  dark,  represent,  respectively,  the 
illuminated  and  the  shaded  side  of  a  mid-rib,  and  the  side-veins  as  well 
are  imitated;  there  are  even  small  scattered  black  spots  resembling 
those  made  on  the  leaf  by  a  species  of  fungus.  Furthermore,  the  butter- 
fly habitually  rests,  not  among  green  leaves,  where  it  would  be  conspicu- 
ous, but  among  leaves  with  which  it  harmonizes  in  coloration. 
Notwithstanding  some  discussion  as  to  whether  it  usually  rests  in  pre 

^9\ 


ADAPTIVE    COLORATION 


195 


cisely  the  same  position  as  a  leaf,  this  insect  certainly  deceives  experi- 
enced entomologists  and  presumably  eludes  birds  and  other  enemies  by 
means  of  its  deceptive  coloration. 

Some  of  the  tropical  Phasmida^  counterfeit  sticks,  green  leaves,  or 
dead  leaves  with  minute  accuracy.     Our  common  phasmids,  Diaphero- 


Fig.   243. — Manomera  hlatchleyi,  on    a  twig. 
Natural  size. 


Fig.  244. — Calocala  lacrymosa;  A,  upper  sur- 
face; B,  with  wings  closed,  and  resting  on  bark. 
Reduced. 


mera  femorata  and  Manomera  hlatchleyi  (Fig.  243),  are  well  known  as 
"stick  insects;"  indeed,  it  is  not  necessary  to  go  beyond  the  temperate 
zone  to  find  plenty  of  examples  of  protective  resemblance.  Geometrid 
caterpillars  imitate  twigs,  holding  the  body  stiffly  from  a  branch  and 
frequently  reproducing  the  form  and  coloration  of  a  twig  with  striking 
exactitude;  and  the  moths  of  the  same  family  are  often  colored  like  the 
bark  against  which  they  spread  their  wings.  Even  more  perfectly  do  the 
Catocala  moths  resemble  the  bark  upon  which  they  rest  (Fig.  244),  with 
their  conspicuous  and  usually  showy  hind  wings  concealed  under  the  pro- 


196 


ENTOMOLOGY 


tectively  colored  front  wings.  The  caterpillars  of  Basilarchia  archippus 
and  Papilio  thoas,  as  well  as  other  larvae  and  not  a  few  moths,  resemble 
closely  the  excrements  of  birds.  Numerous  grass-eating  caterpillars  are 
striped  with  green,  as  is  also  a  sphingid  species  {Ellema  harrisii)  that 
lives  among  pine  needles."  The  large  green  sphinx  caterpillars  (Fig.  66) 
perhaps  owe  their  inconspicuousness  partly  to  their  oblique  lateral 
stripes,  which  cut  a  mass  of  green  into  smaller  areas.  The  caterpillar 
of  Schizura  ipomosce  (Fig.  245),  which  is  green  with  brown  patches,  rests 
for  hours  along  the  eaten  or  torn  edge  of  a  basswood  leaf,  in  which  posi- 


FiG.  245. — Caterpillar  of  Schizura  ipomcea  clinging  to   a  torn  leaf.     Natural  size. 

tion  it  bears  an  extremely  deceptive  resemblance  to  the  partially  dead 
border  of  a  leaf.  The  weevils  that  drop  to  the  ground  and  remain 
immovable  are  often  indistinguishable  to  the  collector  on  account  of 
their  Hkeness  to  bits  of  soil  or  little  pebbles.  Everyone  has  noticed 
the  extent  to  which  some  of  the  grasshoppers  resemble  the  soil  in  color. 
The  CaroHna  locust,  Dissosteira  Carolina,  which  varies  greatly  in 
color,  ranging  from  ashy  gray  to  yellowish  or  to  reddish  brown,  is 
commonly  found  on  soil  of  its  own  color.  Along  the  Atlantic  coast,  the 
seaside  locust,  Trimerotropis  maritima,  is  practically  invisible  against 
the  gray  sand  of  the  seashore,  to  which  it  restricts  itself.  The  same 
species  of  grasshopper  occurs  inland  also,  as  in  Illinois  and  Michigan, 
along  the  shores  of  lakes,  and  is  then  pale  brown,  Hke  the  sands  that  it 


ADAPTIVE    COLORATION 


197 


frequents.  Another  grasshopper  of  the  same  genus,  Trimerotropis 
saxatilis  (Fig.  246)  occurs  only  on  rock-surfaces,  either  bare  or  Hchen- 
crusted.  This  grasshopper,  mottled  with  several  colors  but  especially 
yellow,  black  and  greenish,  is  conspicuous  when  flying  but  indistinguish- 
able when  resting  on  a  patch  of  lichens  (Fig.  246  B) .  Where  the  grass- 
hopper occurs  among  Hchen-covered  rocks,  as  in  southern  IlHnois,  it 
does  not  ahght  by  haphazard  as  a  rule,  but  habitually  flies  from  one 
patch  of  lichens  to  another. 

Instances  such  as  this  give  support  to  the  opinion  that  "protective 
resemblances"  are  not  always  merely  accidental  occurrences;  since  the 
protective  colors  are  rendered  effective  by  special  habits  of  the  insect. 


Pig.   246. — Triynerolropis  saxatilis.     A,  with  wings  of  right  side  spread.     B,  with  wings 
closed,    and    resting    on    lichens.      Natural    size. 


This  particular  grasshopper,  it  may  be  added,  is  sluggish,  and  incKned 
to  remain  where  it  alights — an  advantageous  habit  under  the  circum- 
stances. The  case  is  not  so  simple  as  that  of  a  caterpillar  that  is  green 
simply  because  it  feeds  on  chlorophylls. 

Adventitious  Resemblance. — If,  instead  of  hastily  ascribing  all 
cases  apparently  of  protective  resemblance  to  the  action  of  natural 
selection,  one  inquires  into  the  structural  basis  of  the  resemblance  in 
each  instance,  it  is  found  that  some  cases  can  be  explained,  without  the 
aid  of  natural  selection,  as  being  direct  effects  of  food,  light  or  other 
primary  factors.  Such  cases,  then,  are  in  a  sense  accidental.  For  ex- 
ample, many  inconspicuous  green  insects  are  green  merely  because 
chlorophyll  from  the  food-plant  tinges  the  blood  and  shows  through  the 
skin.  If  it  be  argued  that  natural  selection  has  brought  about  a  thin 
and  transparent  skin,  it  may  be  replied  that  the  skin  of  a  green  cater- 


198  ENTOMOLOGY    " 

pillar  is  by  no  means  exceptional  in  thinness  or  transparency.  More- 
over, many  leaf-mining  caterpillars  are  green,  simply  because  their  food 
is  green;  for,  living  as  they  do  within  the  tissues  of  leaves  and  surrounded 
by  chlorophyll,  their  own  green  color  is  of  no  advantage,  but  is  merely 
incidental. 

Again,  in  the  "protectively"  colored  chrysaHdes  experimented  upon 
by  Poulton,  the  color  was  directly  influenced  by  the  prevailing  color 
of  the  light  that  surrounded  the  larva  during  the  last  few  days  before 
pupation.  Of  course,  it  is  conceivable  that  natural  selection  may  have 
preserved  such  individuals  as  were  most  responsive  to  the  stimulus  of 
the  surrounding  light;  nevertheless  the  fact  remains  that  these  resem- 
blances do  not  demand  such  an  explanation,  which  is,  in  other  words, 
superfluous. 

Indeed,  a  great  many  of  the  assumed  examples  of  "protective  re- 
semblance" are  very  far-fetched.  On  the  other  hand,  when  the  re- 
semblance is  as  specific  and  minutely  detailed  as  it  is  in  the  Kallima 
butterflies — where,  moreover,  special  instincts  are  involved — the  phe- 
nomenon can  scarcely  be  due  to  chance;  the  direct  and  uncombined 
action  of  such  factors  as  food  or  light  is  no  longer  sufiicient  to  explain 
the  facts — although  these  and  other  factors  are  undoubtedly  important 
in  a  primary,  or  fundamental,  way.  Here  natural  selection  becomes 
useful,  as  enabling  us  to  understand  how  original  variations  of  structure 
and  instinct  in  favorable  directions  may  have  been  preserved  and  ac- 
cumulated until  an  extraordinary  degree  of  adaptation  has  been  attained. 

Value  of  Protective  Resemblance.— The  popular  opinion  as  to 
the  efficiency  of  protective  resemblances  is  undoubtedly  an  exaggerated 
one,  owing  mainly  to  the  false  assumption  that  the  senses  of  the  lower 
animals  are  co-extensive  in  range  with  our  own.  As  a  matter  of  fact, 
birds  detect  insects  with  a  facility  far  superior  to  that  of  man,  and 
destroy  them  by  the  wholesale,  in  spite  of  protective  coloration.  Thus, 
as  Judd  has  ascertained,  no  fewer  than  three  hundred  species  of  birds 
feed  upon  protectively  colored  grasshoppers,  which  they  destroy  in 
immense  numbers,  and  more  than  twenty  species  prey  upon  the  twig- 
like geometrid  larvae;  while  the  weevils  that  look  like  particles  of  soil, 
and  the  green-striped  caterpillars  that  assimilate  with  the  surrounding 
foliage  are  constantly  to  be  found  in  the  stomachs  of  birds. 

After  all,  however,  protective  resemblance  may  be  regarded  as  ad- 
vantageous upon  the  whole,  even  if  it  is  ineffectual  in  thousands  of  in- 
stances. An  adaptation  may  be  successful  even  if  it  does  fall  short  of 
perfection;  and  it  should  be  borne  in  mind  that  the  evolution  of  protect- 


ADAPrrV'E    COLORATION  1 99 

ive  resemblances  among  insects  has  probably  been  accompanied  on  the 
part  of  birds  by  an  increasing  ability  to  discriminate  these  insects  from 
their  surroundings. 

Warning  Coloration. — In  strong  contrast  to  the  protectively 
colored  species,  there  are  many  insects  which  are  so  vividly  colored  as 
to  be  extremely  conspicuous  amid  their  natural  surroundings.  Such 
are  many  Hemiptera  (LygcBus,  Murgantia),  Coleoptera  {Necrophorus, 
Lampyridae,  Coccinellidae,  Chrysomelida;),  Hymenoptera  (MutilHdae, 
Vespidie),  and  numerous  caterpillars  and  butterflies.  Conspicuous  col- 
ors, being  frequently — though  not  always — associated  with  qualities 
that  render  their  possessors  unpalatable  or  offensive  to  birds  or  other 
enemies,  are  advantageous  if,  by  insuring  ready  recognition,  they  ex- 
empt their  owners  from  attack. 

Efficiency  of  Warning  Colors. — Owing  to  much  disagreement  as 
to  the  actual  value  of  "warning"  colors,  several  investigators  have  made 
many  observations  and  experiments  upon  the  subject.  Tests  made  by 
offering  various  conspicuous  insects  to  birds,  lizards,  frogs,  monkeys  and 
other  insectivorous  animals  have  given  diverse  results,  according  to 
circumstances.  Thus,  one  gaudy  caterpillar  is  refused  by  a  certain  bird 
at  once,  or  else  after  being  tasted,  but  another  and  equally  showy  cater- 
pillar is  eaten  without  hesitation.  Or,  an  insect  at  first  rejected  may  at 
length  be  accepted  under  stress  of  hunger;  or  a  warningly  colored  form 
disregarded  by  some  animals  is  accepted  by  others.  Moreover,  some 
of  the  experiments  with  captive  insectivorous  animals  are  open  to  ob- 
jection on  the  score  of  artificiality. 

Nevertheless,  from  the  data  now  accumulated,  there  emerge  some 
conclusions  of  definite  value.  Frank  Finn,  whose  conclusions  are  quoted 
beyond,  has  found  in  India  that  the  conspicuous  colors  of  some  butter- 
flies, (Danainae,  Acrcsa,  violce,  Delias  eucharis,  Papilio  aristolochice)  are 
probably  effective  as  "warning"  colors.  Marshall  found  in  South 
Africa  that  mantids,  which  would  devour  most  kinds  of  butterflies,  in- 
cluding warningly  colored  species,  refused  Acrcea,  which  appeared  to  be 
not  only  distasteful  but  even  unwholesome;  Acrcea  is  eaten,  however, 
by  the  predaceous  Asilidse,  which  feed  indiscriminately  upon  insects — 
for  example,  beetles,  dragon  flies  and  even  stinging  Hymenoptera.  The 
masterly  studies  of  Marshall  and  Poulton  strongly  support  the  general 
theory  of  warning  coloration. 

In  this  country,  much  important  evidence  upon  the  subject  has  been 
obtained  by  Dr.  Judd  from  an  extensive  examination  of  the  stomach- 
contents  of  birds,  supplemented  by  experiments  and  field  observations. 


200  ENTOMOLOGY 

Judd  says  that  the  harlequin  cabbage  bug  (Murgantia  histrionica)  and 
other  large  showy  bugs  are  usually  avoided  by  birds;  that  the  showy, 
ill-flavored  lady-beetles  (Coccinellidas)  and  Chrysomelidae  such  as  the 
elm  leaf  beetle,  Diabrotica,  and  Leptinotarsa  (Doryphora),  possess 
comparative  immunity  from  birds;  and  that  Macrodactylus,  Chauliog- 
nathus  and  Cyllene  are  highly  exempt  from  attack.  Such  cases,  he 
adds,  are  comparatively  few  among  insects,  however,  and  in  general, 
warning  colors  are  effective  against  some  enemies  but  ineffective  against 
others. 

Generally  speaking,  hairs,  stings  and  other  protective  devices  are 
accompanied  by  conspicuous  colors — though  there  are  many  exceptions 
to  this  rule.  These  warning  colors  nevertheless  fail  to  accomplish  their 
supposed  purpose  in  the  following  instances,  given  by  Judd.  Taking  in- 
sects that  are  thought  to  be  protected  by  an  offensive  odor  or  a  dis- 
agreeable taste:  Heteroptera  in  general  are  eaten  by  all  insectivorous 
birds,  the  squash  bug  by  hawks  and  the  pentatomids  by  many  birds; 
among  Carabidse  with  their  irritating  fluids,  Harpalus  caliginosus  and 
pennsyhanicus  are  food  for  the  crow,  catbird,  robin  and  six  others; 
Carabus  and  Calosoma  are  relished  by  crows  and  blackbirds;  Silphidae 
are  taken  by  the  crow,  loggerhead  shrike  and  kingbird ;  and  Leptinotarsa 
decemlineata  is  eaten  by  at  least  six  kinds  of  birds:  wood  thrush,  rose- 
breasted  grosbeak,  quail,  crow,  cuckoo  and  catbird.  Of  hairy  and  spiny 
caterpillars,  Arctiidae  are  eaten  by  the  robin,  bluebird,  catbird,  cuckoo 
and  others;  the  larvae  of  the  gipsy  moth  are  food  for  the  blue-jay,  robin, 
chickadee,  Baltimore  oriole  and  many  others  [thirty-one  birds,  in  Massa- 
chusetts]; and  the  spiny  caterpillars  of  Vanessa  antiopa  are  taken  by 
cuckoos  and  orioles.  Of  stinging  Hymenoptera,  bumblebees  are  eaten 
by  the  bluebird,  blue- jay  and  two  flycatchers;  the  honey  bee,  by  the 
wood  pewee,  phoebe,  olive-sided  flycatcher  and  kingbird;  Andrena  by 
many  birds,  and  Vespa  and  Polistes  by  the  red-bellied  woodpecker,  king- 
bird, and  yellow-belhed  flycatcher. 

These  facts  by  no  means  invalidate  the  general  theory,  but  they  do 
show  that  "disagreeable"  qualities  and  their  associated  color  signals 
are  of  httle  or  no  avail  against  some  enemies.  The  weight  of  evidence 
favors  the  theory  of  warning  coloration  in  a  qualified  form.  While  con- 
spicuous colors  do  not  always  exempt  their  owners  from  destruction, 
they  frequently  do  so,  by  advertising  disagreeable  attributes  of  one  sort 
or  another. 

The  evolution  of  warning  coloration  is  explained  by  natural  selec- 
tion; in  fact,  we  have  no  other  theory  to  account  for  it.     The  colors 


ADAPTIVE    COLORATION  .  20I 

themselves  must  have  been  present,  however,  before  natural  selection 
could  begin  to  operate;  their  origin  is  a  question  quite  distinct  from  that 
of  their  subsequent  preservation. 

Protective  Mimicry. — This  interesting  and  highly  involved  phe- 
nomenon is  a  special  form  of  protective  resemblance  in  which  one  species 


Pig. 


-A,  Anosia  plexippus,  the  "model;"   B,  Basilarchia  archippus,   the 
Natural  size. 


imitates  the  appearance  of  another  and  better  protected  species,  there- 
by sharing  its  immunity  from  destruction.  Though  it  attains  its  high- 
est development  in  the  tropics,  mimicry  is  well  illustrated  in  temperate 
regions.  A  familiar  example  is  furnished  by  Basilarchia  archippus 
(Fig.  247,  B),  which  departs  widely  from  the  prevailing  dark  coloration 
of  its  genus  to  imitate  the  milkweed  butterfly,  Anosia  plexippus.  The 
latter  species,  or  "model,"  appears  to  be  unmolested  by  birds,  and  the 
former  species,  or  "mimic,"  is  thought  to  secure  the  same  exemption 


202  ENTOMOLOGY 

from  attack  by  being  mistaken  for  its  unpalatable  model.  The  common 
drone-fly,  Eristalis  tenax  (Fig.  248,  B)  mimics  a  honey  bee  in  form,  size, 
coloration  and  the  manner  in  which  it  buzzes  about  flowers,  in  company 
with  its  model;  it  does  not  deceive  the  kingbird  and  the  flicker,  however. 
Some  Asilidae  (robber  flies)  are  remarkably  hke  bumblebees  in  superfi- 
cial appearance  and  certain  Syrphus  flies  (flower  flies)  mimic  wasps 
with  more  or  less  success.  The  beetle  Casnonia  bears  a  remarkable 
resemblance  to  the  ants  with  which  it  lives. 

The  classic  cases  are  those  of  the  Amazonian  Heliconiidae  and 
Pieridae,  in  which  mimicry  was  first  detected  by  Bates.  The  Heli- 
coniidae are  abundant,  vividly  colored  and  eminently  free  from  the 
attacks  of  birds  and  other  enemies  of  butterflies,  on  account  of  their 


Fig.   248. — Protective  mimicry.     A,  drone  bee,  Apis  melUfera;  B,  drone  fly,  Eristalis  tenax. 

Natural  size. 


disagreeable  odor  and  taste.  Some  of  the  Pieridae — a  family  funda- 
mentally different  from  Hehconiidae — imitate  the  protected  Heliconiidae 
so  successfully,  in  coloration,  form  and  fhght,  that  while  other  Pieridae 
are  preyed  upon  by  many  foes,  the  mimicking  species  tend  to  escape 
attack. 

The  family  Heliconiidae,  referred  to  by  Bates,  comprised  what  are 
now  known  as  the  subfamilies  Heliconiinae,  Ithomiinae  and  Danainae; 
simflarly,  Pieridae  and  Papilionidas  are  now  often  termed  respectively 
Pierinae  and  Papilioninae.  Ithomiinae  are  mimicked  also  by  PapiHo- 
ninae  and  by  moths  of  the  famihes  Castniidae  and  Pericopidae. 

The  discoveries  of  Bates  in  tropical  South  America  were  paralleled 
and  supported  by  those  of  Wallace  in  India  and  the  Malay  Archipelago 
(where  Danainae  are  the  chief  "models"),  and  of  Trimen  in  South  Africa 
(where  Acraeinae  and  Danainae  serve  as  models).  Trimen  discovered  a 
most  remarkable  case,  in  which  three  species  of  Danais  are  mimicked, 
each  by  a  distinct  variety  of  the  feijiale  of  Papilio  cenea  {merope). 


ADAPTR'E    COLORATION  203 

So  much  for  that  kind  of  mimicry — but  how  is  the  following  kind  to 
be  explained?  The  Ithomiinoe  of  the  Amazon  valley  have  the  same 
form  and  coloration  as  the  Heliconiinae,  but  the  Ithomiime  themselves 
are  already  highly  protected.  The  answer  is  that  this  resemblance  is  of 
advantage  to  both  groups,  as  it  minimizes  their  destruction  by  birds — 
these  having  to  learn  but  one  set  of  warning  signals  instead  of  two. 
This  is  the  essence  of  Miiller's  famous  explanation,  which  will  presently 
be  stated  with  more  precision.  There  are  two  kinds  of  mimicry,  then: 
(i)  the  kind  described  by  Bates,  in  which  an  edible  species  obtains 
security  by  counterfeiting  the  appearance  of  an  inedible  species;  (2)  that 
observed  by  Bates  and  interpreted  by  Miiller,  in  which  both  species  are 
inedible.  These  two  kinds  are  known  respectively  as  Batesian  and 
Miillerian  mimicry,  though  some  writers  prefer  to  limit  the  term  mimi- 
cry to  the  Batesian  type. 

Wallace's  Rules. — The  chief  conditions  under  which  mimicry  occurs 
have  been  stated  by  Wallace  as  follows: 

"i.  That  the  imitative  species  occur  in  the  same  area  and  occupy 
the  very  same  station  as  the  imitated. 

"2.  That  the  imitators  are  always  the  more  defenceless. 

"3.  That' the  imitators  are  always  less  numerous  in  individuals. 

"4.  That  the  imitators  differ  from  the  bulk  of  their  aUies. 

"5.  That  the  imitation,  however  minute,  is  external  and  visible 
only,  never  extending  to  internal  characters  or  to  such  as  do  not  affect 
the  external  appearance." 

These  rules  relate  chiefly  to  the  Batesian  form  of  mimicry  and  need 
to  be  altered  to  apply  to  the  Miillerian  kind. 

The  first  criterion  given  by  Wallace  is  evidently  an  essential  one  and 
it  is  sustained  by  the  facts.  It  is  also  true  that  mimic  and  model  occur 
usually  at  the  same  time  of  year;  Marshall  found  many  new  instances 
of  this  in  South  Africa.  In  some  cases  of  mimicry,  strange  to  say,  the 
precise  model  is  unknown.  Thus  some  Nymphalidae  diverge  from  their 
relatives  to  mimic  the  Euploeinae,  though  no  particular  model  has  been 
found.  In  such  instances,  as  Scudder  suggests,  the  prototype  may  exist 
without  having  been  found;  may  have  become  extinct;  or  the  species 
may  have  arrived  at  a  general  resemblance  to  another  group  without 
having  as  yet  acquired  a  likeness  to  any  particular  species  of  the  group, 
the  general  likeness  meanwhile  being  profitable. 

The  second  condition  named  by  Wallace  is  correct  for  Batesian 
but  not  for  Miillerian  mimicry. 

The  fulfilment  of  the  third  condition  is  requisite  for  the  success 


204  ENTOMOLOGY 

of  Batesian  mimicry.  Bates  noted  that  none  of  the  pierid  mimics  were 
so  abundant  as  their  heliconiid  models.  If  they  were,  their  protection 
would  be  less;  and  should  the  mimic  exceed  its  model  in  numbers, 
the  former  would  be  more  subject  to  attack  than  the  latter.  Some- 
times, indeed,  as  Miiller  found,  the  mimic  actually  is  more  common  than 
the  model;  in  which  event,  the  consequent  extra  destruction  of  the 
mimic  would — at  least  theoretically — reduce  its" numbers  back  to  the 
point  of  protection. 

In  Miillerian  mimicry,  however,  the  inevitable  variation  in  abun- 
dance of  two  or  more  converging  and  protected  species  is  far  less  dis- 
astrous; though  when  two  species,  equally  distasteful,  are  involved, 
the  rarer  of  the  two  has  the  advantage,  as  Fritz  Miiller  has  shown.  His 
lucid  explanation  is  essentially  as  follows : 

Suppose  that  the  birds  of  a  region  have  to  destroy  1,200  butter- 
flies of  a  distasteful  species  before  it  becomes  recognized  as  such,  and 
that  there  exist  in  this  region  2,000  individuals  of  species  A  and  10,000 
of  species  B;  then,  if  they  are  different  in  appearance,  each  will  lose 
1,200  individuals,  but  if  they  are  deceptively  alike,  this  loss  will  be  di- 
vided among  them  in  proportion  to  their  numbers,  and  A  will  lose  200 
and  B  1,000.  A  accordingly  saves  1,000,  or  50  per  cent,  of  the  total 
number  of  individuals  of  the  species,  and  B  saves  only  200,  or  2  per  cent. 
Thus,  while  the  relative  numbers  of  the  two  species  are  as  i  to  5,  the 
relative  advantage  from  their  resemblance  is  as  25  to  i. 

If  two  or  more  distasteful  species  are  equally  numerous,  their  re- 
semblance to  one  another  brings  nearly  equal  advantages.  In  cases  of 
this  kind — and  many  are  known — it  is  sometimes  impossible  to  dis- 
tinguish between  model  and  mimic,  as  all  the  participants  seem  to 
have  converged  toward  a  common  protective  appearance,  through  an 
interchange  of  features — the  "reciprocal  mimicry"  of  Dr.  Dixey. 

Marshall  argues,  however,  against  this  diaposematism,  maintaining 
that  in  the  case  of  two  participants  in  Miillerian  mimicry  the  evolution 
of  the  mimetic  pattern  has  been  in  one  direction  only — toward  the  more 
abundant  species — any  variations  in  the  opposite  direction  being  dis- 
advantageous. 

From  this  explanation,  the  superior  value  of  Miillerian  as  compared 
with  Batesian  mimicry  is  evident. 

The  fourth  condition — that  the  imitators  differ  from  the  bulk  of 
their  allies — holds  true  to  such  a  degree  that  even  the  two  sexes  of  the 
same  species  may  differ  extremely  in  coloration,  owing  to  the  fact  that 
the  female  has  assumed  the  likeness  of  some  other  and  protected  species. 


ADAPTIVE    COLORATION  205 

The  female  of  Papilio  cenea,  indeed,  occurs  (as  was  just  mentioned) 
under  three  varieties,  which  mimic  respectively  three  entirely  dis- 
similar species  oiDanais,  and  none  of  the  females  are  anything  like  their 
male  in  coloration. 

The  generally  accepted  explanation  for  these  remarkable  but  numer- 
ous cases  in  which  the  female  alone  is  mimetic,  is  that  the  female,  bur- 
dened with  eggs  and  consequently  sluggish  in  flight  and  much  exposed 
to  attack,  is  benefited  by  imitating  a  species  which  is  immune;  while 
the  male  has  had  no  such  incentive — so  to  speak — to  become  mimetic. 
Of  course,  there  has  been  no  conscious  evolution  of  mimicry. 

Wallace's  fifth  stipulation  is  important,  but  should  read  this  way: 
"The  imitation,  however  minute,  is  but  external  and  visible  usually, 
and  never  extends  to  internal  characters  which  do  not  affect  the  exter- 
nal appearance."     For,  as  Poulton  points  out,  the  alertness  of  a  beetle 
which  mimics  a  wasp,  implies  appropriate  changes  in  the  nervous  and 
muscular  systems.     In  its  intent,  however,  Wallace's  rule  holds  good, 
and  by  disregarding  it  some  writers  strain  the  theory  of  mimicry  be- 
yond reasonable  limits.    Some  have  said,  for  example, 
that  the  resemblance  between  caddis  flies  and  moths      (^^f%     gn^ 
is  mimicry;  when  the  fact  is  that  this  resemblance      iT/^^Sl^ 
is  not  merely  superficial  but  is  deep-seated ;  the  entire        |       |  \^ 

organization  of   Trichoptera   shows   that   they   are      /       N 
closely    related    to    Lepidoptera.     This    likeness  P'^-    249.— a 

^1  ^  •      •  -I      .        re     •.  J        tettigomid,  Myrme- 

expresses,  then,  not  mimicry,  but  ainmty  and  cophana  fail  ax, 
parallel  development.  The  same  objection  applies  ^nt  ""^  TwrcTnatui"! 
to  the  assumed  cases  of  mimicry  within  the  limits  length.  Prom 
of  a  single  family,  as  between  two  genera  of  Heli-  wattenwyl. 
coniidas  or  between  the  chrysomelid  genera  Lema 
and  Diabrotica.  The  more  nearly  two  species  are  related  to  each  other, 
the  more  probable  it  becomes  that  their  similarity  is  due — not  to  mimi- 
cry— but  to  their  common  ancestry. 

On  the  other  hand,  the  resemblance  frequently  occurs  between 
species  of  such  different  orders  that  it  cannot  be  attributed  to  affinity. 
Illustrations  of  this  are  the  mimicry  of  the  honey  bee  by  the  drone  fly, 
and  the  many  other  instances  in  which  stinging  Hymenoptera  are 
counterfeited  by  harmless  flies  or  beetles.  A  tettigoniid  of  the  Sudan 
resembles  an  ant  (Fig.  249),  and  the  resemblance,  by  the  way,  is  ob- 
tained in  a  most  remarkable  manner.  Upon  the  stout  body  of  this 
orthopteron  the  abdomen  of  an  ant  is  delineated  in  black,  the  rest  of 
the  body  being  light  in  color  and  inconspicuous  by  contrast  with  the 


2o6  ENTOMOLOGY 

black.  Indeed  the  various  means  by  which  a  superficial  resemblance  is 
brought  about  between  remotely  related  insects  are  often  extraordinary. 

Irrespective  of  affinity,  insects  of  diverse  orders  may  converge  in 
wholesale  numbers  toward  a  central  protected  form.  The  most  com- 
plete examples  of  this  have  been  brought  to  light  by  Marshall  and 
Poulton,  in  their  splendid  work  on  the  bionomics  of  South  African 
insects,  in  which  is  given,  for  instance,  a  colored  plate  showing  how 
closely  six  distasteful  and  dominant  beetles  of  the  genus  Lycus  are 
imitated  by  almost  forty  species  of  other  genera — a  remarkable  ex- 
ample of  convergence  involving  no  less  than  eighteen  families  and 
five  orders,  namely,  Coleoptera,  Hymenoptera,  Hemiptera,  Lepidoptera 
and  Diptera.  Excepting  a  few  unprotected,  or  Batesian,  mimics  (a  fly 
and  two  or  three  beetles),  this  association  is  one  between  species  that 
are  already  protected,  by  stings,  bad  tastes  or  other  peculiarities. 
In  other  words,  here  is  Miillerian  mimicry  on  an  immense  scale;  and 
if  Miillerian  mimicry  is  profitable  when  only  two  species  are  concerned, 
what  an  enormous  benefit  it  must  be  to  each  of  forty  participants ! 

Strength  of  the  Theory. — Evidently  the  theory  of  mimicry  rests 
upon  the  assumption  that  the  mimics,  by  virtue  of  their  mimicry,  are 
specially  protected  from  insectivorous  foes.  Formerly,  however,  there 
was  altogether  too  little  evidence  bearing  upon  the  assumption  itself, 
though  this  was  supported  by  such  scattered  observations  as  were 
available.  The  oft-repeated  assertion  that  this  lack  of  evidence  was 
due  simply  to  inattention  to  the  subject,  has  been  proved  to  be  true 
by  the  decisive  results  gained  in  the  tropics  by  several  competent 
investigators  who  have  been  able  to  give  the  subject  the  requisite 
amount  of  attention. 

From  his  observations  and  experiments  in  India,  Frank  Finn  con- 
cludes: 

"i.  That  there  is  a  general  appetite  for  butterflies  among  insec- 
tivorous birds,  even  though  they  are  rarely  seen  when  wild  to  attack 
them. 

"2.  That  many,  probably  most,  species  dislike,  if  not  intensely,  at 
any  rate  in  comparison  with  other  butterflies,  the  warningly-colored 
Danainae,  Acraa  viola,  Delias  eucharis,  and  Papilio  aristolochicB;  ot 
these  the  last  being  the  most  distasteful,  and  the  Danainae  the  least  so. 

"3.  That  the  mimics  of  these  are  at  any  rate  relatively  palatable, 
and  that  the  mimicry  is  commonly  effectual  under  natural  conditions. 

''4.  That  each  bird  has  separately  to  acquire  its  experience,  and  well 
remembers  what  it  has  learned. 


ADAPTR'E    COLORATION  207 

"That  therefore  on  the  whole,  the  theory  of  Wallace  and  Bates  is 
supported  by  the  facts  detailed  in  this  and  my  former  papers,  so  far  as 
they  deal  with  birds  (and  with  the  one  mammal  used).  Professor 
Poulton's  suggestion  that  animals  may  be  forced  by  hunger  to  eat  un- 
palatable forms  is  also  more  than  confirmed,  as  the  unpalatable  forms 
were  commonly  eaten  without  the  stimulus  of  actual  hunger — generally, 
also,  I  may  add,  without  signs  of  dislike." 

Though  insects  have  many  vertebrate  and  arthropod  enemies,  it  is 
probable  that  the  evolution  of  mimetic  resemblance,  implying  warning 
coloration,  has  been  brought  about  chiefly  by  insectivorous  birds. 

Neglecting  papers  of  minor  importance,  we  may  pass  at  once  to  the 
most  important  contribution  upon  this  subject — the  voluminous  work 
of  Marshall  and  Poulton  upon  mimicry  and  warning  colors  in  South 
African  insects.  These  investigators  have  found  that  birds  are  to  be 
counted  as  the  principal  enemies  of  butterflies;  that  the  Danainae  and 
Acraeinse,  which  are  noted  as  models,  are  particularly  immune  from  de- 
struction, while  unprotected  forms  suffer;  and  that  mimicking,  though 
palatable,  species  share  the  freedom  of  their  models.  The  same  is  true 
of  beetles,  of  which  Coccinellidse,  Malacodermidse  (notably  Lycus) 
Cantharidae  and  many  Chrysomelidae  serve  as  models  for  many  other 
Coleoptera,  being  "conspicuous  and  constantly  refused  by  insect- 
eaters."  In  short,  the  splendid  work  of  Marshall  and  Poulton  tends  to 
place  the  theory  of  Batesian  and  Miillerian  mimicry  upon  a  substantial 
foundation  of  observational  and  experirnental  evidence. 

In  regard  to  the  important  question — do  birds  avoid  unpalatable 
insects  instinctively  or  only  as  the  result  of  experience — the  evidence  is 
all  one  way.  Several  investigators,  including  Lloyd  Morgan,  have 
found  that  newly-hatched  birds  have  no  instinctive  aversions  as  regards 
food,  but  test  everything,  and  (except  for  some  little  parental  guidance) 
are  obliged  to  learn  for  themselves  what  is  good  to  eat  and  what  is  not. 
This  experimental  evidence  that  the  discrimination  of  food  by  birds  is 
due  solely  to  experience,  was  evidently  highly  necessary  to  place  the 
theory  of  mimicry — especially  the  Miillerian  theory — upon  a  sound 
basis. 

Though  butterflies  as  a  group  are  much  subject  to  the  attacks  of 
birds  in  the  tropics,  it  has  been  asserted  that  butterflies  in  temperate 
regions  are  as  a  whole  almost  exempt  from  the  attacks  of  birds,  and  that 
consequently  the  mimicry  of  the  monarch  (Fig.  247)  by  the  viceroy  is 
of  no  advantage.  In  answer  to  this  assertion  Marshall  has  pubhshed  a 
long  list  of  references  showing  that  butterflies  are  attacked  by  birds 


2o8  ENTOMOLOGY 

more  commonly  than  has  been  generally  supposed.  At  the  same  time 
there  is  no  proof  that  the  viceroy  profits  at  present  by  its  mimetic 
pattern,  though  it  may  have  done  so  in  the  past.  In  any  event,  the 
departure  of  archippus  from  its  congeners  toward  one  of  the  Danainae — a 
famous  group  of  "models"  in  the  tropics — is  unintelligible  except  as  an 
instance  of  mimicry. 

Granting  that  mimicry  is  upon  the  whole  advantageous,  it  becomes 
important  to  learn  just  how  far  the  advantage  extends;  and  we  find  that 
mimicry  is  not  of  universal  effectiveness.  Even  the  highly  protected 
Heliconiinas  and  Danainse  are  food  for  some  predaceous  insects.  In 
this  country,  as  Judd  has  observed,  the  drone-fly  {Eristalis  tenax),  which 
mimics  the  honey  bee,  is  eaten  by  the  kingbird  and  the  phcebe;  the 
kingbird,  indeed,  eats  the  honey  bee  itself,  but  is  said  to  pick  out  the 
drones;  chickens  also  discriminate  between  drones  and  workers,  eating 
the  former  and  avoiding  the  latter.  Bumblebees  and  wasps,  imitated 
by  many  other  insects,  are  themselves  eaten  by  the  kingbird,  catbird 
and  several  other  birds,  though  it  is  not  known  whether  the  stingless 
males  of  these  are  singled  out  or  not.  Such  facts  as  these  do  not  discredit 
the  general  theory  of  mimicry  but  point  out  its  limits. 

Evolution  of  Mimicry. — Natural  selection  gives  an  adequate  ex- 
planation of  the  evolution  of  a  mimetic  pattern.  Before  accepting  this 
explanation,  however,  we  must  inquire:  (i)  What  were  the  first  stages 
in  the  development  of  a  mimetic  pattern?  (2)  What  evidence  is  there 
that  every  step  in  this  development  was  vitally  useful,  as  the  theory  de- 
mands that  it  should  be?  These  pertinent  questions  have  been 
answered  by  Darwin,  Wallace,  Miiller,  Dixey  and  several  other 
authorities. 

The  incipient  mimic  must  have  possessed,  to  begin  with,  colors  or 
patterns  that  were  capable  of  mimetic  development;  evidently  the  raw 
material  must  have  been  present.  Now  Miiller  and  Dixey  in  particular 
have  called  attention  to  the  fact  that  many  pierids  have  at  least  touches 
of  the  reds,  yellows  and  other  colors  that  are  so  conspicuous  in  the  heli- 
coniids.  More  than  this,  however,  Dixey  has  demonstrated — as  appears 
clearly  from  his  colored  figures — a  complete  and  gradual  transition  from 
a  typical  non-mimetic  pierid,  Pieris  locusta,  to  the  mimetic  pierid 
Mylothris  pyrrha,  the  female  of  which  imitates  Heliconius  numata.  He 
traces  the  transition  chiefly  through  the  males  of  several  pierid  species — 
for  the  males,  though  for  the  most  part  white  (the  typical  pierid  color), 
"show  on  the  under  surface,  though  in  varying  degrees,  an  approach 
towards  the  Heliconiine  pattern  that  is  so  completely  imitated  by  their 


ADAPTIVE    COLORATION  209 

mates.  These  partially  developed  features  on  the  under  surface  of  the 
males  enable  us  to  trace  the  history  of  the  growth  of  the  mimetic 
pattern."  Starting  from  Pieris  locusta,  it  is  an  easy  step  to  Mylothris 
lypera,  thence  to  M.  lorena,  and  from  thtfe  to  the  mimetic  M.  pyrrha. 
"Granted  a  beginning,  however  small,  such  as  the  basal  red  touches  in 
the  normal  Pierines,  an  elaborate  and  practically  perfect  mimetic 
pattern  may  be  evolved  therefrom  by  simple  and  easy  stages." 

Furthermore  (in  answer  to  the  second  question),  it  does  not  tax  the 
imagination  to  admit  that  any  one  of  these  color  patterns  has — at  least 
occasionally — been  sufficiently  suggestive  of  the  heliconiid  type  to  pre- 
serve the  hfe  of  its  possessor;  especially  when  both  bird  and  insect  were 
on  the  wing  and  perhaps  some  distance  apart,  when  even  a  momentary 
flash  of  red  or  yellow  from  a  pierid  might  be  enough  to  save  it  from 
attack. 

It  is  highly  desirable,  of  course,  that  this  plausible  explanation 
should  be  tested  as  far  as  possible  by  observations  in  the  field  and  by 
experiments  as  well. 

Mimicry  and  Mendelism. — The  weight  of  evidence  is  at  present 
vastly  in  favor  of  the  theory  of  mimicry  as  against  any  other  explanation 
of  the  facts,  even  though  the  theory  is  sometimes  stretched  to  impossible 
limits  by  some  of  its  enthusiastic  adherents.  The  only  opposing  opinion 
that  has  sufficient  plausibility  to  demand  much  consideration  as  yet 
is  that  of  Punnett. 

In  India  and  Ceylon  the  butterfly  Papilio  polytes  has  in  addition  to 
the  normal  female  a  second  form  of  female  which  mimics  P.  aristolochia 
and  a  third  which  imitates  P.  hector;  polytes  being  palatable  to  birds 
and  its  two  models  unpalatable. 

This  case,  described  by  Wallace  more  than  fifty  years  ago,  is  one  of 
the  classic  examples  of  mimicry.  Punnett  holds,  however,  that  these 
resemblances  are  of  no  practical  value  and  that  natural  selection  htis 
played  no  part  in  the  formation  of  these  polymorphic  forms  and  suggests 
that  Mendehsm  offers  a  better  explanation  of  the  phenomenon— a 
suggestion  that  should  be  tested  experimentally. 

Adaptive  Colors  in  General.— Several  classes  of  adaptive  colors 
have  been  discriminated  and  defined  by  Poulton,  whose  classification, 
necessarily  somewhat  arbitrary  but  nevertheless  very  useful,  is  given 
below,  in  its  abridged  form. 


ENTOMOLOGY 


III. 


APATETIC  COLORS.— Colors  resembling  some  part  of  the  environment  or    the 
appearance  of  another  species. 

A.  Cryptic  Colors. — Protective  and  Aggressive  Resemblances. 

1.  Procryptic    colors. — Protective    Resemblances. — Concealment    as    a    pro- 

tection against  enemies.     Example:  Kallima  butterfly. 

2.  Anticryptic  colors. — Aggressive  Resemblances. — Concealment  in  order  to 

facilitate  attack.     Example:  Mantids  with  leaf-like  appendages. 

B.  PsEUDOSEMATic  COLORS. — False  warning  and  signalling  colors. 

1.  Pseudaposematic  colors.- — Protective  Mimicry.     Example:  Bee-like  fly. 

2.  Psendepisematic    colors. — Aggressive    INIimicry   and   Alluring    Coloration. 

Examples:  Volucella,  resembling  bees  (Fig.  250);  Flower-like  mantid. 
SEMATIC  COLORS.— Warning  and  SignalUng  Colors. 

1.  Aposematic  colors. — Warning  Colors. — Examples:  Gaudy  colors  of  stinging 

insects. 

2.  Episematic  colors. — Recognition  Markings. 
EPIGAMIC  COLORS.— Colors  Displayed  in  Courtship. 


Such  of  these  classes  as  have  not  already  been  discussed  need  brief 
reference. 

Aggressive  Resemblances. — The  resemblance  of  a  carnivorous 
animal  to  its  surroundings  may  not  only  be  protective  but  may  also 


Fig.   250. — Aggressive  mimicry.     On  the  left,  a  bee,  Bombus  maslrucatus;  on  the  right, 
fly,    Volucella    bombylans.     Natural  size. 


enable  it  to  approach  its  prey  undetected,  as  in  the  case  of  the  polar  bear 
or  the  tiger.  Among  insects,  however,  the  occurrence  of  aggressive 
resemblance  is  rather  doubtful,  even  in  the  case  of  the  leaf-Hke  mantids. 

Aggressive  Mimicry. — Under  this  head  are  placed  those  cases  in 
which  one  species  mimics  another  to  which  it  is  hostile.  The  best 
known  instance  is  furnished  by  European  flies  of  the  genus  Volucella  ^ 
whose  larvae  feed  upon  those  of  bumblebees  and  wasps.  The  flies  bear 
a  close  resemblance  to  the  bees,  owing  to  which  it  is  supposed  that  the 
former  are  able  to  enter  the  nests  of  the  latter  and  lay  their  eggs. 

Alluring  Coloration. — The  best  example  of  this  phenomenon  is 
afforded  by  an  Indian  mantid,  Gongylus  gongyloides,  which  resembles  so 
perfectly  the  brightly  colored  flowers  among  which  it  hides  that  insects 
actually  fly  straight  into  its  clutches. 


ADAPTIVE    COLORATION  211 

Recognition  Markings.— Though  these  are  apparently  important 
among  mammals  and  birds,  as  enabling  individuals  of  the  same  species 
quickly  to  recognize  and  follow  one  another,  no  special  markings  for 
this  purpose  are  known  to  occur  among  insects,  not  excepting  the  gre- 
garious migrant  species,  such  as  Anosia  plexippus  and  the  Rocky 
Mountain  locust. 

Epigamic  Colors. — Among  birds,  frequently,  the  bright  colors  of 
the  male  are  displayed  during  courtship,  and  their  evolution  has  been 
attributed  by  Darwin  and  many  of  his  followers  to  sexual  selection — a 
highly  debatable  subject.  Among  insects,  however,  no  such  phenome- 
non has  been  found;  whenever  the  two  sexes  differ  in  coloration  the 
difference  does  not  appear  to  faciHtate  the  recognition  of  even  one  sex 
by  the  other. 

Evolution  of  Adaptive  Coloration. — Natural  selection  is  the  only 
theory  of  any  consequence  that  explains  the  highly  involved  phenomena 
oi  adaptive  coloration.  Against  such  vague  and  unsupported  theories 
as  the  action  of  food,  climate,  laws  of  growth  or  sexual  selection,  natural 
selection  alone  accounts  for  the  multitudinous  and  intricate  correlations 
of  color,  pattern,  form,  attitude,  movement,  place,  time,  etc.,  that  are 
necessary  to  the  development  of  a  perfect  case  of  protective  resemblance 
or  mimicry.  Natural  selection  cannot,  of  course,  originate  colors  or  any 
other  characters,  its  action  being  restricted  to  the  preservation  and 
accumulation  of  such  advantageous  variations  as  may  arise,  from  what- 
ever causes.  As  Poulton  says,  the  vast  body  of  facts,  utterly  meaning- 
less under  any  other  theory,  become  at  once  intelligible  as  they  fall 
harmoniously  into  place  under  the  principle  of  natural  selection,  to 
which,  indeed,  they  yield  the  finest  kind  of  support. 


CHAPTER  VII 

INSECTS  IN  RELATION  TO  PLANTS 

Insects,  in  common  with  other  animals,  depend  for  food  primarily 
upon  the  plant  world.  No  other  animals,  however,  sustain  such  intimate 
and  complex  relations  to  plants  as  insects  do.  The  more  luxuriant  and 
varied  the  flora,  the  more  abundant  and  diversified  is  its  accompanying 
insect  fauna. 

Not  only  have  insects  become  profoundly  modified  for  using  all  kinds 
and  all  parts  of  plants  for  food  and  shelter,  but  plants  themselves  have 
been  modified  to  no  small  extent  in  relation  to  insects,  as  appears  in  their 
protective  devices  against  unwelcome  insects,  in  the  curious  formations 
known  as  "galls,"  the  various  insectivorous  plants,  and  especially  the 
omnipresent  and  often  intricate  floral  adaptations  for  cross-polhnation 
through  the  agency  of  insect  visitors.  .Though  insects  have  laid  plants 
under  contribution,  the  latter  have  not  only  vigorously  sustained  the 
attack  but  have  even  pressed  the  enemy  into  their  own  service,  as  it  were. 

Numerical  Relations. — The  number  of  insect  species  supported  by 
one  kind  of  plant  is  seldom  small  and  often  surprisingly  large.  The 
poison  ivy  {Rhus  toxicodendron)  is  almost  exempt  from  attack,  though 
even  this  plant  is  eaten  by  a  leaf-mining  caterpillar,  two  pyralid  larvae 
and  the  larva  of  a  scolytid  beetle  (Schwarz,  Dyar) .  Horse-chestnut 
and  buckeye  have  perhaps  a  dozen  species  at  most;  elm  has  eighty; 
birches  have  over  one  hundred,  and  so  have  maples;  pines  are  known  to 
harbor  170  species  and  may  jdeld  as  many  more;  while  our  oaks  sustain 
certainly  500  species  of  insects  and  probably  twice  as  many.  Turn- 
ing to  cultivated  plants,  the  clover  is  affected,  directly  or  indirectly,  by 
about  200  species,  including  predaceous  insects,  parasites,  and  flower- 
visitors.  Clover  grows  so  vigorously  that  it  is  able  to  withstand  a  great 
deal  of  injury  from  insects.  Corn  is  attacked  by  about  200  species,  of 
which  50  do  notable  injury  and  some  20  are  pests.  Apple  insects  num- 
ber some  400  species. 

Not  uncommonly,  an  insect  is  restricted  to  a  single  species  of  plant. 
Thus  the  caterpillar  of  Heodes  hypophlceas  feeds  only  on  sorrel  {Rumex 
acetosella),  so  far  as  is  known.  The  chrysomelid  Chrysochus  auratus 
appears  to  be  limited  to  Indian  hemp  {Apocynum  androscemifolium)  and 


INSECTS    IN   RELATION   TO   PLANTS 


213 


to  milkweed  (Asclepias).  In  many  instances  an  insect  feeds  indiffer- 
ently upon  several  species  of  plants  provided  these  have  certain  attri- 
butes in  common.  Thus  Argynnis  cybele,  aphrodite  and  atlantis  eat  the 
leaves  of  various  species  of  violets,  and  the  Colorado  potato  beetle  eats 
different  species  of  Solanum.  Papilio  thoas  feeds  upon  orange,  prickly 
ash  and  other  Rutaceae.  Anosia  plexippus  eats  the  various  species  of 
Asclepias  and  also  Apocynum  androscemifolium;  while  Chrysochus  also 
is  Hmited  to  these  two  genera  of  plants,  as  was  said.  These  plants  agree 
in  having  a  milky  juice;  in  fact  the  two  genera  are  rather  nearly  related 
botanically.  The  common  cabbage  butterfly  {Pieris  rapes)  though  con- 
fined for  the  most  part  to  Cruciferae,  such  as  cabbage,  mustard,  turnip, 

radish,  horse-radish,  etc.,  often  devel-  a       

ops  upon  Tropceolum,  which  belongs  to 
Geraniaceae;  all  its  food  plants,  how- 
ever, have  a  pungent  odor,  which  is 
probably  the  stimulus  to  oviposition. 

Most  phytophagous  insects  range 
over  many  food  plants.  The  cecropia 
caterpillar  has  more  than  sixty  of 
these,  representing  thirty-one  genera 
and  eighteen  orders  of  plants;  and  the 
tarnished  plant  bug  [Lygus  pratensis) 
feeds  indifferently  on  all  sorts  of  herb- 
age, as  does  also  the  caterpillar  of  Dia- 
crisia  virginica.  Many  of  the  insects 
of  apple,  pear,  quince,  plum,  peach, 
and  other  plants  of  the  family  Rosaceae 
occur  also  on  wild  plants  of  the  same 

family;  and  the  worst  of  our  corn  and  wheat  insects  have  come  from 
wild  grasses.  As  regards  number  of  food  plants,  the  gipsy  moth  "holds 
the  record,"  for  its  caterpillar  will  eat  almost  any  plant.  In  Massachu- 
setts, according  to  Forbush  and  Fernald,  it  fed  in  the  field  upon  78 
species  of  plants,  in  captivity  upon  458  species  (30  under  stress  of 
hunger,  the  rest  freely),  and  refused  only  19  species,  most  of  which 
(such  as  larkspur  and  red  pepper)  had  poisonous  or  pungent  juices, 
or  were  otherwise  unsuitable  as  food.  The  migratory  locust  is  noto- 
riously omnivorous,  and  perhaps  eats  even  more  kinds  of  plants  than 
the  gipsy  moth. 

Galls.— Most  of  the  conspicuous  plant  outgrowths  known  as  "galls" 
are  made  by  insects,  though  many  of  the  smaller  plant  galls  are  made 


Pig.  251. — Holcaspis  globulus.     A, 
galls  on  oak,  natural  size;  B,  the  gall- 
maker,  twice  natural  length. 


214 


ENTOMOLOGY 


by  mites  (Acarina)  and  a  few  plant  excrescences  are  due  to  nematode 
worms  and  to  fungi. 

Among  insects,  Cynipidae  (Hymenoptera)  are  pre-eminent  as  gall- 


FiG.  252 


of    Holcaspis   duricoria,    on    oak.      Natural    size. 


makers  and  next  to  these,  Itonididae  (Diptera),  Aphididae  and 
Psyllidae  (Hemiptera) ;  a  few  gall-insects  occur  among  Tenthredinidae 
(Hymenoptera)  and  Trypetidae  (Diptera), 
and  one  or  two  among  Coleoptera  and 
Lepidoptera. 

Cynipidae  affect  the  oaks  (Figs.  251, 
252)  far  more  often  than  any  other  plants, 
though  not  a  few  species  select  the  wild 
rose.  Itonidid  galls  occur  on  a  great 
variety  of  plants,  and  those  of  aphids  on 
elm  (Fig.  253),  poplar,  and  many  other 
plants;  while  psyllid  galls  are  most  fre- 
quent on  hackberry.  The  galls  may  occur 
anywhere  on  a  plant,  from  the  roots  to 
the  flowers  or  seeds,  though  each  gall- 
maker  always  works  on  the  same  part 
of  its  plant, — root,  stem,  bud,  leaf,  leaf- 
vein,  flower,  seed,  etc. 

Galls  present  innumerable  forms,  but 
the  form  and  situation  of  a  gall  are 
usually  characteristic,  so  that  it  is  often 
possible  to  classify  galls  as  species  even  before  the  gall-maker  is  known. 
Gall-Making. — The  female  simply  lays  the  egg  on  the  epidermis,  or 
else  punctures  the  plant  and  deposits  an  egg  in  or  near  the  cambium,  or 
any  other  tissue  capable  of  growth;  the  egg  hatches  and  the  surrounding 
plant  tissue  is  stimulated  to  grow  rapidly  and  abnormally  into  a  gall, 


Pig.  253. — Cockscomb  gall  of 
Colopha  ulmicola,  on  elm.  Slightly 
reduced. 


INSECTS    IN  RELATION    TO    PLANTS  215 

which  serves  as  food  for  the  larva;  this  transforms  within  the  gall  and 
escapes  as  a  winged  insect.  The  physiology  of  gall-formation  is  far 
from  being  understood.  It  has  been  found  that  the  mechanical  irrita- 
tion from  the  ovipositor  is  not  the  initial  stimulus  to  the  development 
of  a  gall;  neither  is  the  fluid  which  is  injected  by  the  female  during 
oviposition,  this  fluid  being  probably  a  lubricant;  if  the  egg  is  removed, 
the  gall  does  not  appear.  Ordinarily  the  gall  does  not  begin  to  grow 
until  the  egg  has  hatched,  and  then  the  gall  grows  along  with  the  larva; 
exceptions  to  this  are  found  in  some  Tenthredinidae  in  which  the  egg  it- 
self increases  in  volume,  when  the  gall  may  grow  with  the  egg.  It 
appears  that  the  larva  exudes  some  fluid  which  acts  upon  the  proto- 
plasm of  certain  plant  cells  (the  cambium  and  other  cells  capable  of 
further  growth  and  multiplication)  in  such  a  way  as  to  stimulate  their 
increase  in  size  and  number.  The  following  observations  on  this  subject 
by  A.  Cosens  are  important.  The  cells  of  the  plant  that  immediately 
surround  the  larva  are  known  as  nutritive  cells.  In  Cynipidae  the 
larva  gradually  withdraws  the  contents  of  these  cells,  by  means  of  the 
mouth  and  not  by  absorption,  and  the  cells  gradually  collapse.  The 
proportion  of  sugar  to  starch  decreases  from  the  inside  of  the  nutritive 
zone  (nearest  the  larva)  to  the  outside.  This  is  owing  to  an  enzyme 
that  changes  starch  into  sugar,  the  source  of  this  enzyme  being  probably 
a  pair  of  salivary  glands  that  open  externally  on  each  side  just  below  the 
mouth  of  the  larva.  The  larva  by  accelerating  the  rate  of  change  from 
starch  to  sugar  renders  available  to  the  plant  more  food  than  usual  and 
therefore  stimulates  the  activity  of  the  protoplasm  toward  greater  cell- 
growth  and  more  rapid  cell-reproduction.  Thus  the  gall  as  well  as  the 
larva  draws  food  from  the  nutritive  zone. 

Why  the  gall  should  have  a  distinctive,  or  specific,  form,  it  is  not  yet 
known.  There  is  no  evidence  that  the  form  is  of  any  adaptive  impor- 
tance, and  the  subject  probably  admits  of  a  purely  mechanical  explana- 
tion. One  factor  in  determining  the  form  of  the  gall  is  the  direction  in 
which  the  stimulus  is  apphed;  a  spherical  cynipid  gall  arising  when  the 
influence  is  about  equally  distributed  in  all  directions  (Cosens) . 

Gall  Insects. — The  study  of  gall  insects  is  in  many  respects  difficult. 
It  is  not  at  all  certain  that  an  insect  which  emerges  from  a  gall  is  the 
species  that  made  it;  for  many  species,  even  of  Cynipidae,  make  no  galls 
themselves  but  lay  their  eggs  in  galls  made  by  other  species.  Such 
guest-insects  are  termed  inquilines.  Furthermore,  both  gall-makers 
and  inquihnes  are  attacked  by  parasitic  Hymenoptera,  making  the  in- 
terrelations of  these  insects  hard  to  determine.     Many  species  of  insects 


2l6  ENTOMOLOGY 

feed  upon  the  substance  of  galls;  thus  Sharp  speaks  of  as  many  as  thirty 
different  kinds  of  insects,  belonging  to  almost  all  the  orders,  as  having 
been  reared  from  a  single  species  of  gall. 

Parthenogenesis  and  Alternation  of  Generations. — Parthenogenesis 
has  long  been  known  to  occur  among  Cynipidae.  It  has  repeatedly 
been  found  that  of  thousands  of  insects  emerging  from  galls  of  the 
same  kind,  all  were  females.  In  one  such  instance  the  females  were 
induced  by  Adler  to  lay  eggs  on  potted  oaks,  when  it  was  found  that  the 
resulting  galls  were  quite  unlike  the  original  ones,  and  produced  both 
sexes  of  an  insect  which  had  up  to  that  time  been  regarded  as  another 
species.  Besides  parthenogenesis  and  this  alternation  of  generations, 
many  other  complications  occur,  making  the  study  of  gall-insects  an 
intricate  and  highly  interesting  subject. 

Plant-Enemies  of  Insects. — Most  of  the  flowering  plants  are  com- 
paratively helpless  against  the  attacks  of  insects,  though  there  are  many 
devices  which  preveint  "unwelcome"  insects  from  entering  flowers,  for 
instance  the  sticky  calyx  of  the  catchfly  {Silene  virginica),  which 
entangles  ants  and  small  flies.  A  few  plants,  however,  actually  feed 
upon  insects  themselves.  Thus  the  species  of  Drosera,  as  described  in 
Darwin's  classic  volume  on  insectivorous  plants,  have  specialized  leaves 
for  the  purpose  of  catching  insects.  The  stout  hairs  of  these  leaves  end 
each  in  a  globular  knob,  which  secretes  a  sticky  fluid.  When  a  fly 
ahghts  on  one  of  these  leaves  the  hairs  bend  over  and  hold  the  insect; 
then  a  fluid  analogous  to  the  gastric  juice  of  the  human  stomach  exudes, 
digests  the  albuminoid  substances  of  the  insect  and  these  are  absorbed 
into  the  tissues  of  the  leaf;  after  which  the  tentacles  unfold  and  are 
ready  for  the  next  insect  visitor.  The  Venus's  flytrap  is  another  well 
known  example;  the  trap,  formed  from  the  terminal  portion  of  a  leaf, 
consists  of  two  valves,  each  of  which  bears  three  trigger-like  bristles, 
and  when  these  are  touched  by  an  insect  the  valves  snap  together  and 
frequently  imprison  the  insect,  which  is  eventually  digested,  as  before. 
In  the  common  pitcher-plants,  the  pitcher,  fashioned  from  a  leaf,  is  lined 
with  downward  pointing  bristles,  which  allow  an  insect  to  enter  but 
prevent  its  escape.  The  bottom  of  the  pitcher  contains  water,  in 
which  ma^  be  found  the  remains  of  a  great  variety  of  insects  which 
have  drowned.  There  are  even  nectar  glands  and  conspicuous  colors, 
presumably  to  attract  insects  into  these  traps,  where  their  decomposi- 
tion products  are  more  or  less  useful  to  the  plant.  In  Pinguicula  the 
margin  of  a  leaf  rolls  over  and  envelops  insects  that  have  been  caught 
by  the  glandular  hairs  of  the  upper  surface  of  the  leaf,  a  copious  secretion 


INSECTS    IN   RELATION   TO   PLANTS 


217 


digests  the  softer  portions  of  the  insects,  and  the  dissolved  nitrogenous 
matter  is  absorbed  into  the  plant.  Utricularia  has  little  bladders  which 
entrap  small  aquatic  insects.  These  plants  are  only  partially  dependent 
on  insect-food,  however,  for  they  all  possess  chlorophyll. 

Bacteria  cause  epidemic  diseases  among  insects,  as  in  the  flacherie 
of  the  silkworm;  and  fungi  of  a  few  groups  are  spe- 
cially  adapted   to   develop  in  the  bodies  of  living  fl 
insects. 

Those  who  rear  insects  know  how  frequently 
caterpillars  and  other  larvae  are  destroyed  by  fungi 
that  give  the  insects  a  powdered  appearance.  These 
fungi,  referred  to  the  genus  Isaria,  are  in  some  cases 
known  to  be  asexual  stages  of  forms  of  Cordyceps, 
which  forms  appear  from  the  bodies  of  various  larvae, 
pupae  and  imagines  as  long,  conspicuous,  fructifying 
sprouts  (Fig.  254). 

The  chief  fungous  parasites  of  insects  belong  to 
the  large  family  Entomophthoracese,  represented  by 
the  common  Empusa  nmsccB  (Fig.  255)  which  affects 
various  flies.  In  autumn,  especially  in  warm  moist 
weather,  the  common  house  fly  may  often  be  seen 
in  a  dead  or  dying  condition,  sticking  to  a  window- 
pane,  its  abdomen  distended  and  presenting  alter- 
nate black  and  white  bands,  while  around  the  fly 
at  a  little  distance  is  a  white  powdery  ring,  or  halo. 
The  white  intersegmental  bands  are  made  by  threads 

of  the  fungus  just  named,  and  the  white  halo  by 

countless  asexual  spores   known  as   conidia,  which 

have   been   forcibly    discharged    from    the    swollen 

threads  that  bore  them  (Fig.  255)  by  pressure,  result- 
ing probably  from  the  absorption  of  moisture.    These 

spores,  ejected  in  all  directions,  may  infect  another 

fly  upon  contact  and  produce  a  growth  of  fungus 

threads,  or  hyphcE,  in  its  body.     The  fungus  may  be  propagated  also 

by  means  of  resting  spores,  as  found  by  Thaxter,  our  authority  on  the 

fungi  of  insects. 

Empusa  aphidis  is  very  common  on  plant  lice  and  is  an  important 

check  upon  their  multipHcation.     Aphids  killed  by  this  fungus  are 

found  cUnging  to  their  food  plant,  with  the  body  swollen  and  discolored. 

Empusa  grylli  attacks  crickets,  grasshoppers,  caterpillars  and  other 


Pig.  254. — Fruc- 
tifying sprouts .  of 
a  fungus,  Cordyceps 
ravenelit,  a  r  i  s'i  n  g 
from  the  body  of  a 
white  grub,  Lachno- 
sterna.  Slightly 
reduce  d. — A  f  t  e  r 
Riley. 


2l8 


ENTOMOLOGY 


forms.  Curiously  enough,  grasshoppers  affected  by  this  fungus  almost 
always  crawl  to  the  top  of  some  plant  and  die  in  this  conspicuous  position. 
Sporotrichum,  a  genus  of  hyphomycetous  fungi,  affects  a  great 
variety  of  insects,  spreading  within  the  body  of  the  host  and  at  length 
emerging  to  form  on  the  body  of  the  insect  a  dense  white  felt-like 
covering,  this  consisting  chiefly  of  myriads  of  spores,  by  means  of  which 
healthy  insects  may  become  infected.  Under  favorable  conditions, 
especially  in  moist  seasons,  contagious  fungous  diseases  constitute  one 
of  the  most  important  checks  upon  the  increase  of  insects  and  are 
therefore  of  vast  economic  importance.     Thus  the  termination  (in  i^ 


Fig.  255. — Empusa  mtisccB,  the  common  fly-fungus.  A,  house  fly  (Musca  domeslica), 
surrounded  by  fungus  spores  (conidia) ;  B,  group  of  conidiophores  showing  conidia  in 
several  stages  of  development;  C,  basidium  [h)  bearing  conidium  (c)  before  discharge. 
B  and  C  after  Th.\xter. 


of  a  disastrous  outbreak  of  the  chinch  bug  in  Illinois  and  neighboring 
states  "was  apparently  due  chiefly,  if  not  altogether,  to  parasitism  by 
fungi."  Artificial  cultures  of  the  common  Sporotrichum  glohulijerum 
have  been  used  extensively  as  a  means  of  spreading  infection  among 
chinch  bugs  and  grasshoppers,  with,  however,  but  moderate  success. 
Transmission  of  Diseases  of  Plants.— Not  a  few  bacterial  and  fun- 
gous diseases  of  plants  are  known  to  be  transmitted  by  insects.  M.  B. 
Waite  proved  experimentally  that  the  bacillus  causing  fire  blight  of 
pear,  apple  and  other  pomaceous  trees  is  carried  by  honey  bees  and 
other  insects  from  flower  to  flower,  multiplies  in  the  nectar,  and  enters  the 
host  plant.  Bees,  wasps  and  flies  obtain  the  bacilli  from  the  exudation 
from  old  cankers  and  carry  the  organisms  either  to  blossoms  or  to  young 


INSECTS    IN    RELATION    TO    PLANTS  219 

growing  shoots.  Other  investigators  have  found  that  apple  aphids, 
leafhoppers,  the  tarnished  plant  bug  {Lygus  pratensis)  and  the  shot-hole 
borer  {Scolytus  rugulosus)  are  also  responsible  for  the  inoculation  of 
fruit  trees  with  the  bacilli  of  blight. 

Dr.  E.  F.  Smith  demonstrated  that  cucurbit  wilt  is  spread,  probably 
exclusively,  by  insects,  particularly  the  striped  and  the  twelve-spotted 
cucumber  beetles  {Diahrotica  vittata  and  D.  duodecim punctata,  respect- 
ively), which  introduce  the  bacilli  of  the  disease  into  the  plants  as  they 
feed.  Some  of  the  beetles  carry  the  bacillus  over  winter,  in  the  alimen- 
tary tract,  and  infect  young  plants  with  the  wilt  in  spring. 

The  spores  of  the  fungous  disease  known  as  brown  rot  of  peach  and 
plum  are  probably  carried  by  bees,  wasps  and  certain  other  insects, 
and  introduced  into  wounds  in  the  fruits  made  by  themselves  or  other 
insects.  The  plum  curculio  almost  certainly  leaves  these  spores  in 
punctures  that  it  makes. 

Cankers  of  Leptosphceria  on  apple  bark  occur  around  the  oviposition 
wounds  made  by  tree-crickets  {(Ecanthus),  and  it  has  been  shown  experi- 
mentally that  these  insects  convey  the  spores  of  the  disease  both 
externally  and  internally  and  inoculate  them  into  the  host  plant. 
Typical  cankers  on  apple  branches  have  been  obtained  artficially  by 
inoculation  with  feces  of  tree-crickets  fed  on  spores  of  the  disease. 

The  mosaic  diseases  of  cucumber,  potato  and  tobacco  are  trans- 
mitted by  plant  lice.  The  spores  of  bitter  rot  of  apples  are  conveyed 
from  decaying  apples  to  sound  fruits  by   pomace  flies  (Drosophila). 

Insects  in  Relation  to  Flowers. — Among  the  most  marvelous  phe- 
nomena known  to  the  biologist  are  the  innumerable  and  complex 
adaptations  by  means  of  which  flowers  secure  cross  pollination  through 
the  agency  of  insect  visitors.  Cross  fertilization  is  actually  a  necessity 
for  the  continued  vigor  and  fertility  of  flowering  plants,  and  while  some 
of  them  are  adapted  for  cross  pollination  by  wind  or  water,  the  majority 
of  flowering  plants  exhibit  profound  modifications  of  floral  structure  for 
compelling  insects  (and  a  few  other  animals,  as  birds  or  snails)  to  carry 
pollen  from  one  flower  to  another.  '  In  general,  the  conspicuous  colors 
of  flowers  are  for  the  purpose  of  attracting  insects,  as  are  also  the  odors 
of  flowers.  Night-blooming  flowers  are  often  white  or  yellow  and  as  a 
rule  strongly  scented.  Colors  and  odors,  however,  are  simply  indica- 
tions to  insects  that  edible  nectar  or  pollen  is  at  hand.  Such  is  the 
usual  statement,  and  it  is  indeed  probable  that  insects  actually  do  asso- 
ciate color  and  nectar,  even  though  they  will  fly  to  bits  of  colored  paper 
almost  as  readily  as  they  will  to  flowers  of  the  same  colors.     It  is  not 


2  20  ENTOMOLOGY 

to  be  supposed,  however,  that  insects  feahze  that  they  confer  any  benefit 
upon  the  plant  in  the  flowers  of  which  they  find  food.  At  any  rate, 
most  flowers  are  so  constructed  that  certain  insects  cannot  get  the 
nectar  or  pollen  without  carrying  some  pollen  away,  and  cannot  enter 
the  next  flower  of  the  same  kind  without  leaving  some  of  this  pollen 
upon  the  stigma  of  that  flower.  Take  the  iris,  for  example,  which  is 
admirably  adapted  for  pollination  by  a  few  bees  and  flies. 

Iris. — In  the  common  blue-flag  {Iris  versicolor,  Fig.  256)  each  of  the 


Fig.  256. — Bumblebee    (Bo7nbiis)    entering  flower  of  blue-flag  (Iris  versicolor).     Slightly 

reduced. 


three  drooping  sepals  forms  the  floor  of  an  arched  passageway  leading 
to  the  nectar.  Over  the  entrance  and  pointing  outward  is  a  movable 
lip  (Fig.  257,  /),  the  outer  surface  of  which  is  stigmatic.  An  entering 
bee  hits  and  bends  down  the  free  edge  of  this  lip,  which  scrapes  pollen 
from  the  back  of  the  insect  and  then  springs  back  into  place.  Within 
the  passage,  the  hairy  back  of  the  bee  rubs  against  an  overhanging 
anther  (an)  and  becomes  powdered  with  grains  of  pollen  as  the  insect 
pushes  down  towards  the  nectar.     As  the  bee  backs  out  of  the  passage 


INSECTS    IN    RELATION    TO    PLANTS 


it  encounters  the  guardian  lip  again,  but  as  this  side  of  the  lip  cannot 
receive  pollen,  immediate  close  pollination  is  prevented.  Of  course, 
it  is  possible  for  bees  to  enter  another  part  of  the  same  flower  or  another 
flower  of  the  same  plant,  but  as  a  matter  of  fact,  they  habitually  fly 
away  to  another  plant;  moreover,  as  Darwin  found,  foreign  pollen  is 
prepotent  over  pollen  from  the  same  flower.  It  may  be  added  that 
bees  and  other  poUenizing  insects  ordi- 
narily visit  in  succession  several  flowers 
of  the  same  kind. 

Orchids. — The  orchids,  with  their 
fantastic  forms,  are  really  elaborate 
traps  to  insure  cross  pollination.  In 
some  orchids  {Hahenaria  and  others) 
the  nectar,  lying  at  the  bottom  of  a 
long  tube,  is  accessible  only  to  the  long- 
tongued  Sphingidae.  While  probing  for 
the  nectar,  a  sphinx  moth  brings  each 
eye  against  a  sticky  disk  to  which  a 
pollen  mass  is  attached,  and  flies  away 
carrying  the  mass  on  its  eye.  Then 
these  pollinia  bend  down  on  their  stalks 
in  such  a  way  that  when  the  moth 
thrusts  its  head  into  the  next  flower 
they  are  in  the  proper  position  to 
encounter  and  adhere  to  the  stigma. 
The  orchid  Angr cecum  sesquipedale,  of 
Madagascar,  has  a  nectary  tube  more 

than  eleven  inches  long,  from  which  Darwin  inferred  the  existence  of  a 
sphinx  moth  with  a  tongue  equally  long. 

Milkweed. — The  various  milkweeds  are  fascinating  subjects  to  the 
student  of  the  interrelations  of  flowers  and  insects.  The  flowers,  like 
those  of  orchids,  are  remarkably  formed  with  reference  to  cross  pollina- 
tion by  insects.  As  a  honey  bee  or  other  insect  crawls  over  the  flowers 
(Fig.  258,  yl)  to  get  the  nectar,  its  legs  slip  in  between  the  pecuUar  nec- 
tariferous Jwods  situated  in  front  of  each  anther.  As  a  leg  is  drawn  up- 
ward one  of  its  claws,  hairs,  or  spines  frequently  catches  in  a  V-shaped 
fissure  (/,  Fig.  258,  B)  and  is  guided  along  a  sHfto  a  notched  disk,  or  cor- 
puscle (Fig.  258,  C,  d).  This  disk  cHngs  to  the  leg  of  the  insect,  which 
carries  off  by  means  of  the  disk  a  pair  of  pollen  masses,  or  pollinia  (Fig. 
258,  C).     When  first  removed  from  their  enclosing  pockets,  or  anthers, 


Fig.  257. — Section  to  illustrate 
cross  pollination  of  Iris,  an,  anther; 
I,  stigmatic  lip;  n,  nectary;  s,  sepal. 


222  ENTOMOLOGY 

these  thin  spatulate  pollinia  lie  each  pair  in  the  same  plane,  but  in  a  few 
seconds  the  two  pollinia  twist  on  their  stalks  and  come  face  to  face  in 
such  a  way  that  one  of  them  can  be  easily  introduced  into  the  stigmatic 
chamber  of  a  new  flower  visited  by  the  insect.  Then  the  struggles  of  the 
insect  ordinarily  break  the  stem,  or  retinaculum,  of  the  poUinium  and 
free  the  insect.  Often,  however,  the  insect  loses  a  leg  or  else  is  per- 
manently entrapped,  particularly  in  the  case  of  such  large-flowered 
milkweeds  as  Asclepias  cornuti,  which  often  captures  bees,  flies  and 
moths  of  considerable  size.     Pollination  is  accomplished  by  a  great 


Fig.  258. — Structure  of  milkweed  flower  (Asclepias  incarnata)  with  reference  to  cross 
pollination.  A,  a  single  flower;  c,  corolla;  h,  hood;  B,  external  aspect  of  fissure  (/)  leading 
up  to  disk  and  also  into  stigmatic  chamber;  h,  hood;  C,  pollinia;  d,  disk.     Enlarged. 


variety  of  insects,  chiefly  Hymenoptera,  Diptera,  Lepidoptera  and 
Coleoptera.  These  insects  when  collected  about  milkweed  flowers 
usually  display  the  pollinia  dangUng  from  their  legs,  as  in  Fig.  259. 

The  details  of  pollination  may  be  gathered  by  a  close  observer  from 
observations  in  the  field  and  may  be  demonstrated  to  perfection  by  using 
a  detached  leg  of  an  insect  and  dragging  it  upward  between  two  of  the 
hoods  of  a  flower;  first  to  remove  the  pair  of  pollinia  and  then  again 
to  introduce  one  of  them  into  an  empty  stigmatic  chamber. 

Yucca. — An  extraordinary  example  of  the  interdependence  of  plants 
and  insects  was  made  known  by  Riley,  whose  detailed  account  is  here 
summarized.  The  yuccas  of  the  southern  United  States  and  Mexico 
are  among  the  few  plants  that  depend  for  pollination  each  upon  a  single 
species  of  insect.  The  pollen  of  Yucca  filamentosa  cannot  be  introduced 
into  the  stigmatic  tube  of  the  flower  without  the  help  of  a  Httle  white 


INSECTS    IN    RELATION    TO    PLANTS 


Fig.  259. — A  wasp,  Spliex  ichneu- 
mon e  a,  with  pollinia  of  milkweed 
attached  to  its  legs.     Slightly  enlarged. 


tineid  moth,  Proniiha  yuccasella,  the  female  of  which  pollenizes  the  flower 
and  lays  eggs  among  the  ovules,  that  her  larvae  may  feed  upon  the  young 
seeds.  While  the  male  has  no  unusual  structural  peculiarities,  the 
female  is  adapted  for  her  special  work 
by  modifications  which  are  unique 
among  Lepidoptera,  namely,  a  pair 
of  prehensile  and  spinous  maxillary 
"tentacles"  (Fig.  260,  A)  and  a  long 
protrusible  ovipositor  {B)  which  com- 
bines in  itself  the  functions  of  a  lance 
and  a  saw. 

The  female  begins  to  work  soon 
after  dark,  and  will  continue  her  opera- 
tions even  in  the  light  of  a  lantern. 
Clinging  to  a  stamen  (Fig.  261)  she 
scrapes  off  pollen  with  her  palpi  and 
shapes  it  into  a  pellet  by  using  the  front  legs.  After  gathering  pollen 
from  several  flowers  she  flies  to  another  flower,  as  a  rule,  thrusts  her 
long  flexible  ovipositor  into  the  ovary  (Fig.  262)  and  lays  a  slender  egg 

alongside  seven  or  eight  of 
the  ovules.  After  laying  one 
or  more  eggs  she  ascends  the 
pistil  and  actually  thrusts 
pollen  into  the  stigmatic  tube 
and  pushes  it  in  firmly.  The 
ovules  develop  into  seeds, 
some  of  which  are  consumed 
by  the  larvae,  though  plenty 
are  left  to  perpetuate  the 
plant  itself.  Three  species 
of  Pronuha  are  known,  each 
restricted  to  particular 
species  of  Yucca.  Riley  says 
that  Yucca  never  produces 
seed  where  Pronuba  does  not 
occur  or  where  she  is  excluded 
artificially,  and  that  artificial 
pollination  is  rarely  so  suc- 


FiG.  260. — Pronuha  yuccasella.  A,  maxillary 
tentacle  and  palpus;  B,  ovipositor. — After  Riley. 
Figures  260-262  are  republished  from  the  Third 
Report  of  the  Missouri  Botanical  Garden,  by 
permission. 


cessful  as  the  normal  method. 
Why  does  the  insect  do  this? 


The  little  nectar  secreted  at  the  base 


224 


ENTOMOLOGY 


of  the  pistil  appears  to  be  of  no  consequence,  at  present,  and  the  stig- 
matic  fluid  is  not  nectarian;  indeed,  the  tongue  of  Pronuha,  used  in 
clinging  to  the  stamen,  seems  to  have  lost  partially  or  entirely  its 
sucking  power,  and  the  alimentary  canal  is  regarded  as  functionless. 
Ordinarily  it  is  the  flower  which  has  become  adapted  to  the  insect, 
which  is  enticed  by  means  of  pollen  or  nectar,  but  here  is  a  flower  which — 
though  entomophilous  in  general  structure — has  apparently  adapted 
itself  in  no  way  to  the  single  insect  upon  which  it  is  dependent  for  the 
continuance  of  its  existence.     More  than  this,  the  insect  not  only  labors 


Fig.  261. — Pronuha  yuccasella, 
female,  gathering  pollen  from  anthers 
of  Yucca.     Enlarged. 


Fig.  262. 


-Pronuha  moth  ovipositing  in  flower  of 
Yucca.     Slightly  reduced. 


without  compensation  in  the  way  of  food,  but  has  even  become  highly 
modified  with  reference  to  the  needs  of  the  plant, — its  special  modifica- 
tions being  unparalleled  among  insects  with  the  exception  of  bees,  and 
being  more  puzzHng  than  the  more  extensive  adaptations  of  the  bees 
when  we  take  into  consideration  the  impersonal  nature  of  the  operations 
of  Pronuha.  Further  investigation  may  render  these  extraordinary 
interrelations  more  intelligible  than  they  are  at  present. 

The  bogus  Yucca  moth  {Prodoxus  quinquepunctella)  closely  resembles 
and  associates  with  Pronuha  but  oviposits  in  the  flower  stalks  of  Yucca 
and  has  none  of  the  special  adaptive  structures  found  in  Pronuha. 

As  regards  floral  adaptations,  these  examples  are  sufi&cient  for  pres- 
ent purposes;  many  others  have  been  described  by  the  botanist;  in  fact, 
the  adaptations  for  cross  pollination  by  insects  are  as  varied  as  the 
flowers  themselves. 


INSECTS    IN   RELATION   TO   PLANTS 


225 


Insect  Pollenizers.— The  great  majority  of  entomophilous  flowers 
are  pollenized  by  bees  of  various  kinds;  the  apple,  pear,  blackberry, 
raspberry  and  many  other  rosaceous  plants  depend  chiefly  upon  the 
honey  bee,  while  clover  cannot  set  seed  without  the  aid  of  bumblebees 
or  honey  bees,  assisted  by  wild  bees  such  as  Tetralonia  and  Melissodes. 
LiUes  and  orchids  frequently  employ  butterflies  and  moths,  as  well  as 
bees,  and  the  milkweed  is  adapted  in  a  remarkable  manner  for  pollination 
by  butterflies,  moths  and  some  wasps,  as  was  described.  Honeysuckle, 
lilac,  azalea,  tobacco.  Petunia,  Datura  and  many  other  strongly  scented 
and  conspicuous  nocturnal  flowers  attract  for  their  own  uses  the  long- 
tonged  sphinx  moths  (Fig.  263) ;  the  evening  primrose,  like  milkweed, 
is  a  favorite  of  noctuid  moths. 
UmbeUiferous  plants  are  pollen- 
ized chiefly  by  various  flies,  but 
also  by  bees  and  wasps.  Pond 
lilies,  golden  rod  and  some  other 
flowers  are  pollenized  largely  by 
beetles,  though  the  flowers  exhibit 
no  special  modifications  in  relation 
to  these  particular  insects.  It  is 
noteworthy  that  polhnation  is  per- 
formed only  by  the  more  highly 
organized  insects,  the  bees  head- 
ing the  list. 

Of  all  the  insects  that  haunt  the 
same  flower,  it  frequently  happens 
that  only  a  few  are  of  any  use  to  the 
flower  itself;  many  come  for  pollen 

only;  many  secure  the  nectar  illegitimately;  thus  bumblebees  puncture 
the  nectaries  of  columbine,  snapdragon  and  trumpet  creeper  from  the 
outside,  and  wasps  of  the  genus  Odynerus  cut  through  the  corolla  of 
Pentestemon  Icevigatus,  making  a  hole  opposite  each  nectary;  then  there 
are  the  many  insects  that  devour  the  floral  organs,  and  the  insects  which 
are  predaceous  or  parasitic  upon  the  others.  In  the  Iris,  according  to 
Needham,  two  small  bees  {Clisodon  terminalis  and  Osmia  distincta)  are 
the  most  important  pollenizers,  and  next  to  them  a  few  syrphid  flies, 
while  bumblebees  also  are  of  some  importance.  The  beetle  Trichius 
piger  and  several  small  flies  obtain  pollen  without  assisting  the  plant, 
and  Pamphila,  Eudatnus,  Chrysophanus  and  some  other  butterflies 
succeed  after  many  trials  in  stealing  the  nectar  from  the  outside  (Fig. 


Pig.   263. — Protoparce  sexla  visiting   flower 
of  Petunia.     Reduced. 


2  26  ENTOMOLOGY 

264).  A  weevil  {Mononychus  vulpeculus)  punctures  the  nectary,  and 
the  flowing  nectar  then  attracts  a  great  variety  of  insects.  Grass- 
hoppers and  caterpillars  eat  the  flowers,  an  ortalid  fly  destroys  the  buds, 
and  several  parasitic  or  predaceous  insects  haunt  the  plant ;  in  all,  more 
than  sixty  species  of  insects  are  concerned  in  one  way  or  another  with 
the  Iris. 


Fig.  264. — A  butterfly,  Polites  peckius,  stealing  nectar  from  a  flower  of  Iris  versicolor. 
Slightly  reduced. 

Modifications  of  Insects  with  Reference  to  Flowers. — While  the 
manifold  and  exquisite  adaptations  of  the  flower  for  cross  polhnation 
have  engaged  universal  attention,  very  little  has  been  recorded  con- 
cerning the  adaptations  of  insects  in  relation  to  flowers.  In  fact, 
the  adaptation  is  largely  one-sided;  flowers  have  become  adjusted  to 
the  structure  of  insects  as  a  matter  of  vital  necessity — to  put  it  that 
way — while  insects  have  had  no  such  urgent  need — so  to  speak — in  rela- 
tion to  floral  structure.  They  have  been  influenced  by  floral  structure  to 
some  extent  however,  and  in  some  cases  to  a  very  great  extent,  as  ap- 
pears from  their  structural  and  physiological  adaptations  for  gathering 
and  using  pollen  and  nectar. 


INSECTS    IN   RELATION   TO   PLANTS 


227 


Among  mandibulate  insects,  beetles  and  caterpillars  that  eat  the 
floral  envelopes  show  no  special  modifications  for  this  purpose;  pollen- 
feeding  beetles,  however,  usually  have  the  mouth  parts  densely  clothed 
with  hairs,  as  in  Euphoria  (Fig.  265).  In  suctorial  insects,  the  mouth 
parts  are  frequently  formed  with  reference  to  floral  structure;  this  is 
the  case  in  many  butterflies  and  particularly  in  Sphingidae,  in  which  the 
length  of  the  tongue  bears  a  direct  relation  to  the  depth  of  the  nectary 
in  the  flowers  that  they  visit.  According  to  MiiUer,  the  mouth  parts  of 
Syrphida?,  Stratyomyiidae  and  Muscidae  are  specially  adapted  for  feed- 


FiG.  265. — A,  right  mandible;  B,  right  maxilla;  C,  hypo- 
pharynx,  of  a  pollen-eating  beetle.  Euphoria  inda.  Enlarged. 
(The  mandibles  are  remarkable  in  being  two-lobed.) 


Fig.  266. — Pollen-gath- 
ering hair  from  a  worker 
honey  bee,  with  a  pollen 
grain  attached.  Greatly 
magnified. 


ing  on  pollen.  In  Apidae,  the  tongue  as  compared  with  that  of  other 
Hymenoptera,  is  exceptionally  long,  enabling  the  insect  to  reach  deep 
into  a  flower,  and  is  exquisitely  specialized  (Fig.  129)  for  lapping  up 
and  sucking  in  nectar. 

Pollen-gathering  flies  and  bees  collect  pollen  in  the  hairs  of  the  body 
or  the  legs ;  these  hairs,  especially  dense  and  often  twisted  or  branched 
(Figs.  266,  91)  to  hold  the  pollen,  do  not  occur  on  other  than  pollen- 
gathering  species  of  insects.  Caudell  found  that  out  of  200  species  of 
Hymenoptera  only  23  species  had  branched  hairs  and  that  these  species 
belonged  without  exception  to  the  pollen-gathering  group  Anthophila, 
no  representative  of  which  was  found  without  such  hairs.     Similar 


228 


ENTOMOLOGY 


branched  hairs  occur  also  on  the  flower-frequenting  Bombyliidae  and 
Syrphidae. 

The  most  extensive  modifications  in  relation  to  flowers  are  found  in 
Fronuba,  as  already  described,  and  above  all  in  Apidae,  especially  the 
honey  bee. 

Honey  Bee.- — The  thorax  and  abdomen  and  the  bases  of  the  legs 
are  clothed  with  flexible  branching  hairs  (Fig.  266),  which  entangle 


Fig.  267. — Adaptive  modifications  of  the  legs  of  the  worker  honey  bee.  A,  outer 
aspect  of  left  hind  leg;  B,  portion  of  left  middle  leg;  C,  inner  aspect  of  tibio-tarsal  region  of 
left  hind  leg;  D,  tibio-tarsal  region  of  left  fore  leg;  a,  antenna  comb;  au,  auricle;  b,  brush; 
c,  coxa;  co,  corbiculum;/,  femur;  p,  pecten;  pc,  pollen  combs;  s,  spur;  sp,  spines;  ss,  spines;  t, 
trochanter;  ii,  tibia;  v,  velum;  w,  so-called  wax  pincers;  1-5,  tarsal  segments;  i,  metatarsus, 
or  planta. 


pollen  grains.  These  are  combed  out  of  the  gathering  hairs  by  means 
of  special  pollen  combs  (Fig.  267,  C,  pc)  on  the  inner  surface  of  the 
planta  of  the  hind  tarsus,  the  middle  legs  also  assisting  in  this  operation. 
From  these  combs,  the  pollen  is  transferred  to  the  pollen  baskets,  or 
corbicula  (Fig.  267,  A,  co),  of  the  outer  surface  of  each  hind  tibia,  the 
pollen  from  one  side  being  transferred  to  the  corbiculum  of  the  opposite 
side.  This  is  accomplished  in  the  following,  manner:  the  left  pecten 
combs  out  the  pollen  from  the  right  planta  and  a  mass  of  pollen  forms 
just  above  the  left  pecten  at  the  lower  end  of  the  corbiculum;  this  mass 
.  gradually  grows  larger  and  is  pushed  up  along  the  corbiculum  by  the 


INSECTS    IN   RELATION   TO   PLANTS  229 

upward  movement  of  the  auricle:  Further  details  are  given  by  Casteel, 
whose  admirably  precise  and  thorough  studies  on  the  manipulation  of 
pollen  and  wax  by  the  honey  bee  have  corrected  certain  prevalent 
errors  and  added  much  to  our  knowledge  of  the  subject.  Arriving  at 
the  nest,  the  hind  legs  are  thrust  into  a  cell  and  the  mass  of  pollen  on 
each  corbiculum  is  pried  out  by  means  of  a  spur  situated  at  the  apex 
of  the  middle  tibia  (Fig.  267,  B,  s),  this  lever  being  slipped  in  at  the 
upper  end  of  the  corbiculum  and  then  pushed  along  the  tibia  under  the 
mass  of  pollen;  the  spur  is  used  also  in  cleaning  the  wings,  which  ex- 
plains its  presence  on  queen  and  drone,  as  well  as  worker,  but  the  pollen- 
gathering  structures  of  the  hind  legs  are  confined  to  the  worker. 
The  so-called  wax-pincers  of  the  hind  legs  (Fig.  267,  A,  C,  w)  at  the 
tibio-tarsal  articulation,  have  nothing  to  do  with  the  transfer  of  wax 
scales  from  the  abdomen  to  the  mouth,  according  to  Casteel;  a  wax  scale 
being  removed  from  its  pocket  by  becoming  impaled  on  stiff  spines 
at  the  distal  end  of  the  inner  face  of  the  planta. 

For  cleaning  the  antennae,  a  front  leg  is  passed  over  an  antenna, 
which  slips  into  a  semicircular  scraper  (Fig.  267,  D,  a)  fashioned  from 
the  basal  segment  of  the  tarsus;  when  the  leg  is  bent  at  the  tibio-tarsal 
articulation,  an  appendage,  or  velum  {v)  of  the  tibia  falls  into  place  to 
complete  a  circular  comb,  through  which  the  antenna  is  drawn.  This 
comb  is  itself  cleaned  by  means  of  a  brush  of  hairs  (6)  on  the  front  margin 
of  the  tibia.  A  series  of  erect  spines  (sp)  along  the  anterior  edge  of  the 
first  tarsal  segment  is  used  as  an  eye  brush,  to  remove  pollen  grains  or 
other  foreign  bodies  from  the  hairs  of  the  compound  eyes.  The  labium 
and  maxillae  (Fig.  56)  are  exquisitely  constructed  with  reference  to 
gathering  and  sucking  nectar;  the  maxillae  are  used  also  to  smooth  the 
cell  walls  of  the  comb;  the  mandibles  (Fig.  56,  md),  notched  in  queen 
and  drone  but  with  a  sharp  entire  edge  in  the  worker,  are  used  for  cut- 
ting, scraping  and  moulding  wax,  as  well  as  for  other  purposes.  The 
entire  digestive  system  of  the  honey  bee  is  adapted  in  relation  to  nectar 
and  pollen  as  food;  the  proventriculus  forms  a  reservoir  for  honey  and 
is  even  provided  at  its  mouth  with  a  rather  complex  apparatus  for  strain- 
ing the  honey  from  the  accompanying  pollen  grains,  as  described  by 
Cheshire.  The  wax  glands  (Fig.  104)  are  remarkable  speciahzations  in 
correlation  with  the  food  habits,  as  are  also  the  various  cephaHc  glands, 
the  chief  functions  of  which  are  given  as:  (i)  digestion,  as  the  conversion 
of  cane  sugar  into  grape  sugar,  and  possibly  starch  into  sugar;  (2)  the 
chemical  alteration  of  wax;  (3)  the  production  of  special  food  substances, 
which  are  highly  important  in  larval  development. 


230 


ENTOMOLOGY 


Numerous  special  sensory  adaptations  also  occur.  In  fact,  the 
whole  organization  of  the  honey  bee  has  become  profoundly  modified 
in  relation  to  nectar  and  pollen.  Many  other  insects  have  the  same 
food  but  none  of  them  sustain  such  intimate  relations  to  the  flowers  as 
do  the  bees. 

Ant-plants. — There  are  several  kinds  of  tropical  plants  which  are 
admirably  suited  to  the  ants  that  inhabit  them.  Indeed,  it  is  often  as- 
serted that  these  plants  have  become  modified  with  special  reference  to 
their  use  by  ants,  though  this  is  a  gratuitous  and  improbable  assumption. 

Belt  found  several  species  of  Acacia  in  Nicaragua  and  the  Amazon 
valley  which  have  large  hollow  stipular  thorns,  inhabited  by  ants  of  the 
genus  Pseudomyrma.     The  ants  enter  by  boring  a  hole  near  the  apex  of 


Fig.  268. — Acacia  sphcerocephala,  an  ant-plant,  b,  one  of  the  "  Belt's  bodies";  g,  gland; 
s,  s,  hollow  stipular  thorns,  perforated  by  ants.  Reduced. — From  Strasburger's  Lehrbiich 
der  Botanik. 


a  thorn  (Fig.  268,  s).  The  plant  affords  the  ants  food  as  well  as  shelter, 
for  glands  ig)  at  the  bases  of  the  petioles  secrete  a  sugary  fluid,  while 
many  of  the  leaflets  are  tipped  with  small  egg-shaped  or  pear-shaped 
appendages  {h)  known  as  "Belt's  bodies,"  which  are  rich  in  albumin, 
fall  off  easily  at  a  touch,  and  are  eaten  by  the  ants.  These  ants  drive 
away  the  leaf-cutting  species,  incidentally  protecting  the  tree  in  which 
they  live. 

The  ant- trees  {Cecropia  adenopus)  of  Brazil  and  Central  America 
have  often  been  referred  to  by  travelers.  When  one  of  these  trees  is 
handled  roughly,  hosts  of  ants  rush  out  from  small  openings  in  the  stems 
and  pugnaciously  attack  the  disturber.  Just  above  the  insertion  of 
each  leaf  is  a  small  pit  (Fig.  269,  a,  b)  where  the  wall  is  so  thin  as  to  form 
a  mere  diaphragm,  through  which  an  ant  (probably  a  fertilized  female) 
bores  and  reaches  a  hollow  internode.  To  establish  communication  be- 
tween the  internodal  chambers,  the  ants  bore  through  the  intervening 


INSECTS    IN    RELATION    TO    PLANTS 


23] 


septa  (Fig.  270).  They  seldom  leave  the  Cecropia  plant,  unless  dis- 
turbed, and  even  keep  herds  of  aphids  in  their  abode.  The  base  of  each 
petiole  bears  (Fig.  271)  tender  little  egg-like  bodies  ("Miiller's  bodies") 
which  the  ants  detach,  store  away  and  eat ;  the  presence  of  these  bodies 
is  a  sure  sign  that  the  tree  is  uninhabited  by  these  ants,  which,  by  the 
way,  belong  to  the  genus  Azteca. 

It  is  too  much  to  assert  that  the  ants  protect  the  Cecropia  plant  in 
return  for  the  food  and  shelter  which  they  obtain.     All  ants  are  hostile 


Fig.  269. — Portion  of  young  stem  of  Cecropia  aden- 
opus  showing  internodal  pits,  o  and  b.  Natural  size. 
Figures  269-271  are  from  Schimper's  Pflanzengeo- 
graphie. 


Fig.  270. — Cecropia  adenopus. 
Portion  of  a  stem,  split  so  as  to 
show  internodal  chambers  and  the 
intervening  septa  perforated  by 
ants. 


to  all  other  species  of  ants,  with  few  exceptions,  and  even  to  other  col- 
onies of  their  own  species;  so  that  their  assaults  upon  leaf-cutting  ants 
are  by  no  means  special  and  adaptive  in  their  nature,  and  any  protec- 
tion that  a  plant  derives  therefrom  is  merely  incidental.  Furthermore, 
hollow  stems,  glandular  petioles  and  pitted  stems  are  of  common 
occurrence  when  they  bear  no  relation  to  the  needs  of  ants.  These 
interrelations  of  ants  and  plants  are  too  often  misinterpreted  in 
popular  and  uncritical  accounts  of  the  subject. 

The  interesting  habits  of  the  leaf-cutting  ants  in  relation  to  the 


ENTOMOLOGY 


plants  that  they  attack  are  described  in  a  subsequent  chapter,  where 
will  be  found  also  an  account  of  the  Harvesting  ants. 

The  epiphytic  plants  Myrmecodia  and  Hydnophytum,  of  Java,  form 


/ 

Fig.  271. — Cecropiaadenopus.     Base  of  Fig.   272. — Hydnophytum  monlannm.     Sec- 

petiole      showing     "Muller's     bodies."    tionof  pseudo-bulb,  to  show  chambers  inhabited 
Slightly  reduced.  by    ants.     One-fourth    natural    size. — A  f  t  e  r 

FOREL. 


spongy  bulb-like  masses,  the  chambers  of  which  are  usually  tenanted  by 
ants,  which  rush  forth  when  disturbed.  These  lumps  (Fig.  272)  are 
primarily  water-reservoirs,  but  the  ants  utilize  them  by  boring  into  them 
and  from  one  chamber  into  another.  In  plants  of  the  genus  Humholdtia 
the  ants  can  enter  the  hollow  internodes  through  openings  that  already 
exist. 


CHAPTER  VIII 

INSECTS  IN  RELATION  TO  OTHER  AXIM.VLS 

On  the  one  hand,  insects  may  derive  their  food  from  other  animals, 
either  living  or  dead;  on  the  other  hand,  insects  themselves  are  food  for 
other  animals,  especially  fishes  and  birds,  against  which  they  protect 
themselves  by  various  means,  more  or  less  effective.  These  topics  form 
the  principal  subject  of  the  present  chapter. 

Predaceous  Insects. — Innumerable  aquatic  insects  feed  largely  or 
entirely  upon  microscopic  Protozoa,  Rotifera,  Entomostraca,  etc.;  this 
is  especially  the  case  with  culicid  (mosquito)  and  chironomid(  midge) 
larvae.  Many  aquatic  Hemiptera  and  Coleoptera  prey  upon  planarians, 
nematodes,  annelids,  molluscs  and  crustaceans;  Belostoma  (the  electric 
light  bug)  sometimes  pierces  the  bodies  of  tadpoles  and  small  fishes; 
Dytiscus  also  kills  young  fishes  occasionally  and  is  distinctly  carnivorous 
both  as  larva  and  imago.  Among  terrestrial  insects,  the  ground  beetles, 
Carabidae,  are  notably  predaceous,  preying  not  only  upon  other  insects 
but  also  upon  molluscs,  myriopods,  mites  and  spiders.  Ants  do  not 
hesitate  to  attack  all  kinds  of  animals;  in  the  tropics  the  wandering 
ants  (Eciton)  attack  lizards,  rats  and  other  vertebrates,  and  it  is  said 
that  even  huge  serpents,  when  in  a  torpid  condition,  are  sometimes 
killed  by  armies  of  these  pugnacious  insects. 

Mosquitoes  affect  not  only  mammals  but  also,  though  rarely,  fishes 
and  turtles.  The  gadflies  (Tabanidae)  torment  horses  and  cattle  by 
their  punctures;  and  the  black-flies,  or  buffalo  gnats  {Simulium),  per- 
secute horses,  mules,  cattle,  fowls,  and  frequently  become  unendurable 
even  to  man.  The  notorious  tsetse  fly  {Glossina  morsitans)  of  South 
Africa  spreads  a  deadly  disease  among  horses,  cattle  and  dogs,  by  inocu- 
lating them  with  a  protozoan  blood-parasite,  to  the  effects  of  which, 
.fortunately,  man  is  not  susceptible. 

Parasitic  Insects. — Insects  belonging  to  several  diverse  orders  have 
become  peculiarly  modified  to  exist  as  parasites  either  upon  or  within 
the  bodies  of  birds  or  mammals. 

Almost  all  birds  are  infested  by  Mallophaga,  or  bird  lice,  of  which 
Kellogg  has  catalogued  264  species  from  257  species  of  North  American 
birds.     Sometimes  a  species  of  Mallophaga  is  restricted  to  a  single 


234  ENTOMOLOGY 

species  of  bird,  though  in  the  majority  of  cases  this  is  not  so.  Several 
mallophagan  species  often  infest  a  single  bird;  thus  nine  species  occur 
on  the  hen,  and  no  less  than  twelve"  species,  representing  five  genera,  on 
the  American  coot.  These  parasites  spread  by  contact  from  male  to 
female,  from  old  to  young,  and  from  one  bird  to  another  when  the  birds 
are  gregarious.  When  a  single  species  of  bird  louse  occurs  on  two  or 
more  hosts,  these  are  almost  always  closely  allied,  and  Kellogg  has  sug- 
gested the  interesting  possibility  that  such  a  species  has  persisted  un- 
changed from  a  host  which  was  the  common  ancestor  of  the  two  or  more 
present  hosts.  Mallophaga  are  not  altogether  limited  to  birds,  how- 
ever, for  they  may  be  found  on  cattle,  horses,  cats,  dogs,  and  some  other 
mammals;  Kellogg  records  eighteen  species  from  fifteen  species  of  mam- 
mals. These  biting  lice  feed,  not  upon  blood,  but  upon  epidermal 
cells  and  portions  of  feathers  or  hairs.  They  have  fiat  tough  bodies 
(Fig.  i8),  with  no  traces  of  wings,  and  a  large  head  with  only  simple  eyes; 
the  eggs  are  glued  to  feathers  or  hairs. 

Mammals  only  are  infested  by  the  sucking  lice,  or  Pediculidae. 
These  (Fig.  24)  have  a  large  oval  or  rounded  abdomen,  no  wings,  a 
small  head,  minute  simple  eyes  or  none,  and  claws  that  are  adapted  to 
clutch  hairs;  the  eggs  are  glued  to  hairs.  Sucking  Hce  affect  horses, 
cattle,  sheep,  dogs,  monkeys,  seals,  elephants,  etc.,  and  man  is  para- 
sitized by  three  species,  namely,  the  head  louse  (Pediculus  humanus 
capitis),  the  body  louse  {Pediculus  humanus  corporis),  and  the  crab 
louse  {Phthirius  pubis) . 

An  anomalous  beetle,  Platypsyllus  castoris,  occurs  throughout  North 
America  and  also  in  Europe  as  a  parasite  of  the  beaver. 

The  iieas,  allied  to  Diptera  but  constituting  a  distinct  order  (Siphon- 
aptera),  are  familiar  parasites  of  chickens,  cats,  dogs  and  human  beings. 
These  insects  (Fig.  32)  are  well  adapted  by  their  laterally  compressed 
bodies  for  slipping  about  among  hairs,  and  their  saltatory  powers  and 
general  elusiveness  are  well  known.  Their  wings  are  reduced  to  mere 
rudiments,  their  eyes  when  present  are  minute  and  simple  and  their 
mouth  parts  are  suctorial. 

Among  Diptera,  there  are  a  few  external  parasites,  the  best  known 
of  which  is  the  sheep  tick  {Melophagus  ovinus),  though  several  highly 
interesting  but  little-studied  forms  are  parasitic  upon  birds  and  bats. 

The  larvae  of  the  bot-flies  (CEstridae)  are  common  internal  parasites 
of  mammals.  The  sheep  bot-fly  {CEstrus  avis)  deposits  her  eggs  or 
larvae  on  the  nostrils  of  sheep;  the  maggots  develop  in  the  frontal  sinuses 
of  the  host,  causing  vertigo  or  even  death,  and  when  full  grown  escape 


INSECTS    IN   RELATION   TO   OTHER   ANIMALS  235 

through  the  nostrils  and  pupate  in  the  soil.  The  horse  bot-fly  {Gastro- 
philus  equi)  glues  its  eggs  to  the  hairs  of  horses,  especially  on  the  fore 
legs  and  shoulders,  whence  the  larvae  are  licked  off  and  swallowed;  once 
in  the  stomach,  the  bots  fasten  themselves  to  its  lining,  by  means  of 
special  hooks,  and  withstand  almost  all  efforts  to  dislodge  them ;  though 
when  the  bots  have  attained  their  growth  they  release  their  hold  and 
pass  with  the  excrement  to  the  soil.  Bots  of  the  genus  Hypoderma  form 
tumors  on  cattle  and  other  mammals,  domesticated  or  wild.  The  ox- 
warble  (//.  lineata,  Fig.  213,  /)  reaches  the  oesophagus  of  its  host  in  the 
same  manner  as  the  horse  bot,  according  to  Curtice,  but  then  makes 
its  way  into  the  subcutaneous  tissue  and  causes  the  well-known  tumors 
on  the  back  of  the  animal;  when  full  grown  the  bots  squirm  out  of  these 
tumors  and  drop  to  the  ground,  leaving  permanent  holes  in  the  hide. 

Parasitism  in  General. — Parasitic  insects  evidently  do  not  consti- 
tute a  phylogenetic  unit,  but  the  parasitic  habit  has  arisen  independently 
in  many  different  orders.  These  insects  do,  however,  agree  superficially, 
in  certain  respects,  as  the  result  of  what  may  be  termed  convergence  of 
adaptation.  Thus  a  dipterous  larva,  living  as  an  internal  parasite,  in 
the  presence  of  an  abundant  supply  of  food,  has  no  legs,  no  eyes  or  anten- 
nae, and  the  head  is  reduced  to  a  mere  rudiment,  sufficient  simply  to 
support  a  pair  of  feeble  jaws;  the  skin,  moreover,  is  no  longer  armor-like 
but  is  thin  and  delicate,  the  body  is  compact  and  fleshy,  and  the  diges- 
tive system  is  of  a  simplified  type.  The  same  modifications  are  found  in 
hymenopterous  larvae,  under  similar  food-conditions,  except  that  the 
head  undergoes  less  reduction.  The  various  external  parasites  lack 
wings,  almost  invariably,  and  the  eyes,  instead  of  being  compound, 
are  either  simple  or  else  absent.  In  some  special  cases,  as  in  a  few 
dipterous  parasites  of  birds  and  bats,  the  wings  are  present,  either 
permanently  or  only  temporarily,  enabhng  the  insects  to  reach  their 
hosts. 

This  so-called  parasitic  degeneration,  widespread  among  animals  in 
general  and  consisting  chiefly  in  the  reduction  or  loss  of  locomotor  and 
sensory  functions  in  correlation  with  an  immediate  and  plentiful  supply 
of  food,  results  in  a  simplicity  of  organization  which  is  to  be  regarded — 
not  as  a  primitive  condition — but  as  an  expression  of  what  is,  in  one 
sense,  a  high  degree  of  specialization  to  peculiar  conditions  of  life. 
This  exquisite  degree  of  adaptation  to  a  special  environment,  however, 
sacrifices  the  general  adaptability  of  the  animal, — makes  it  impossible 
for  a  parasite  to  adapt  itself  to  new  conditions;  and  while  parasitism 
may  be  an  immediate  advantage  to  a  species,  there  are  few  parasites 


236  ENTOMOLOGY 

that  have  attained  any  degree  of  dominance  among  animals.  Ichneu- 
monidas,  to  be  sure,  are  remarkably  dominant  among  insects,  but  their 
parasitic  adaptations  are  limited  for  the  most  part  to  the  larval  stage, 
and  the  adults  may  be  said  to  be  as  free  for  new  adaptations  as  are  any 
other  Hymenoptera. 

Scavenger  and  Carrion  Insects. — Not  a  few  families  of  Diptera 
and  Coleoptera  derive  their  food  from  dead  animal  matter.  The 
aquatic  families  Dytiscidae  and  Gyrinidae  are  largely  scavengers. 
Among  terrestrial  forms,  Silphidae  feed  on  dead  animals  of  all  kinds; 
the  burying  beetles  (Necrophorus),  working  in  pairs,  undermine  and 
bury  the  bodies  of  birds,  frogs  and  other  small  animals,  and  lay  their 
eggs  in  the  carcasses;  Histeridae  and  Staphylinidae  are  carrion  beetles, 
and  Dermestidae  attack  dried  animal  matter  of  almost  every  description, 
their  depredations  upon  furs,  feathers,  museum  specimens,  etc.,  being 
famihar  to  all.  Ants  are  famous  as  scavengers,  destroying  decaying 
organic  matter  in  immense  quantities,  particularly  in  the  tropics. 
Many  Scarabaeidae  feed  upon  excrementitious  matter,  for  example  the 
"tumble-bugs,"  which  are  frequently  seen  in  pairs,  laboriously  rolUng 
along  or  burying  a  large  ball  of  dung,  which  is  to  serve  as  food  for  the 
larva. 

Insects  as  Food  for  Vertebrates.— Lizards,  frogs,  and  toads  are 
insectivorous,  especially  toads.  The  American  toad  feeds  chiefly  upon 
insects,  which  form  77  per  cent,  of  its  food  for  the  season,  the  remainder 
consisting  of  myriopods,  spiders,  Crustacea,  molluscs  and  worms,  accord- 
ing to  the  observations  of  A.  H.  Kirkland,  who  states  that  Lepidoptera 
form  28  per  cent,  of  the  total  insect  food,  Coleoptera  27,  Hymenoptera 
19  and  Orthoptera  3  per  cent.  The  toad  does  not  capture  dead  or 
motionless  insects  but  uses  its  extensile  sticky  tongue  to  Kck  in  moving 
insects  or  other  prey,  which  it  captures  with  surprising  speed  and  preci- 
sion. In  the  cities  one  often  sees  many  toads  under  an  arc-light  engaged 
in  catching  insects  that  fall  anywhere  near  them.  Though  its  diet  is 
varied  and  somewhat  indiscriminate,  the  toad  consumes  such  a  large 
proportion  of  noxious  insects,  such  as  May  beetles  and  cutworms,  that 
it  is  unquestionably  of  service  to  man. 

Moles  are  entirely  insectivorous  and  destroy  large  numbers  of  white 
grubs  and  caterpillars;  field  mice  and  prairie  squirrels  eat  many  insects, 
especially  grasshoppers,  and  the  skunk  revels  in  these  insects,  though  it 
eats  beetles  frequently,  as  does  also  the  raccoon,  which  is  to  some  extent 
insectivorous.  Monkeys  are  omnivorous  but  devour  many  kinds  of 
insects. 


INSECTS    IN    RELATION    TO    OTHER    ANIMALS  237 

With  these  hasty  references,  we  may  pass  at  once  to  the  subject  of 
the  insect  food  of  fishes  and  birds. 

Insects  in  Relation  to  Fishes. — Insects  constitute  the  most  impor- 
tant portion  of  the  food  of  adult  fresh  water  fishes,  furnishing  forty 
per  cent,  of  their  food,  according  to  Dr.  Forbes,  from  whose  valuable 
writings  the  following  extracts  are  taken. 

"The  principal  insectivorous  fishes  are  the  smaller  species,  whose 
size  and  food  structures,  when  adult,  unfit  them  for  the  capture  of  Ento- 
mostraca,  and  yet  do  not  bring  them  within  reach  of  fishes  or  Mollusca. 
Some  of  these  fishes  have  peculiar  habits  which  render  them  especially 
dependent  upon  insect  Hfe,  the  Httle  minnow  Phenacohius,  for  example, 
which,  according  to  my  studies,  makes  nearly  all  its  food  from  insects 
(ninety-eight  per  cent.)  found  under  stones  in  running  water.  Next  are 
the  pirate  perch,  Aphredoderus  (ninety-one  per  cent.),  then  the  darters 
(eighty-seven  per  cent.),  the  croppies  (seventy-three  per  cent.),  half- 
grown  sheepshead  (seventy-one  p&c  cent.),  the  shovel  fish  (fifty-nine  per 
cent.),  the  chub  minnow  (fifty-six  per  cent.),  the  black  warrior  sunfish 
{ChcBnohryttus)  and  the  brook  silversides  (each  fifty-four  per  cent.) ,  and 
the  rock  bass  and  the  cyprinoid  genus  Notropis  (each  fifty-two  per 
cent.). 

"Those  which  take  few  insects  or  none  are  mostly  the  mud-feeders 
and  the  ichthyophagous  species,  Amia  (the  dog-fish)  being  the  only 
exception  noted  to  this  general  statement.  Thus  we  find  insects  wholly 
or  nearly  absent  from  the  adult  dietary  of  the  burbot,  the  pike,  the  gar, 
the  black  bass,  the  wall-eyed  pike,  and  the  great  river  catfish,  and  from 
that  of  the  hickory  shad  and  the  mud-eating  minnows  (the  shiner,  the 
fathead,  etc.).  It  is  to  be  noted,  however,  that  the  larger  fishes  all  go 
through  an  insectivorous  stage,  whether  their  food  when  adult  be  almost 
wholly  other  fishes,  as  with  the  gar  and  the  pike,  or  molluscs,  as  with  the 
sheepshead.  The  mud-feeders,  however,  seem  not  to  pass  through  this 
stage,  but  to  adopt  the  limophagous  habit  as  soon  as  they  cease  to 
depend  upon  Entomostraca. 

"Terrestrial  insects,  dropping  into  the  water  accidentally  or  swept 
in  by  rains,  are  evidently  diHgently  sought  and  largely  depended  upon 
by  several  species,  such  as  the  pirate  perch,  the  brook  minnow,  the  top 
minnows  or  kilHfishes  (cyprinodonts)  the  toothed  herring  and  several 
cyprinoids  {Semotilus,  Pimephales  and  Notropis). 

"Among  aquatic  insects,  minute  slender  dipterous  larvse,  belonging 
mostly  to  Chironomus,  Corethra  and  allied  genera  are  of  remarkable 
importance,  making,  in  fact,  nearly  one  tenth  of  the  food  of  all  the  fishes 


238  ENTOMOLOGY 

studied.  They  are  most  abundant  in  Phenacohius  and  Etheostoma, 
which  genera  have  become  especially  adapted  to  the  search  for  these 
insect  forms  in  shallow  rocky  streams.  Next  I  found  them  most  gener- 
ally in  the  pirate  perch,  the  brook  silversides,  and  the  stickleback,  in 
which  they  averaged  forty-five  per  cent.  They  amounted  to  about  one 
third  the  food  of  fishes  as  large  and  important  as  the  red  horse  and  the 
river  carp,  and  made  nearly  one  fourth  that  of  fifty-one  buffalo  fishes. 
They  appear  further  in  considerable  quantity  in  the  food  of  a  number  of 
the  minnow  family  {Notropis,  Fimephales,  etc.),  which  habitually  fre- 
quent the  swift  waters  of  stony  streams,  but  were  curiously  deficient  in 
the  small  collection  of  miller's  thumbs  (Cottidae)  which  hunt  for  food  in 
similar  situations.  The  sunfishes  eat  but  few  of  this  important  group, 
the  average  of  the  family  being  only  six  per  cent. 

''Larvae  of  aquatic  beetles,  notwithstanding  the  abundance  of  some 
of  the  forms,  occurred  in  only  insignificant  ratios,  but  were  taken  by 
fifty-six  specimens,  belonging  to  nineteen  of  the  species,— more  fre- 
quently by  the  sunfishes  than  by  any  other  group.  The  kinds  most 
commonly  captured  were  larvae  of  Gyrinidae  and  Hydrophilidae ;  where- 
as the  adult  surface  beetles  themselves  {Gyrinus,  Dineutes,  etc.) — whose 
zigzag-darting  swarms  no  one  can  have  failed  to  notice — were  not  once 
encountered  in  my  studies. 

"The  almost  equally  well-known  slender  water-skippers  [Gerris]  seem 
also  completely  protected  by  their  habits  and  activity  from  capture 
by  fishes,  only  a  single  specimen  occurring  in  the  food  of  all  my  specimens. 
Indeed,  the  true  water  bugs  (Hemiptera)  were  generally  rare,  with  the 
exception  of  the  small  soft-bodied  genus  Corixa  which  was  taken  by 
one  hundred  and  ten  specimens,  belonging  to  twenty-seven  species, 
— most  abundantly  by  the  sunfishes  and  top  minnows. 

"From  the  order  Neuroptera  [in  the  broad  sense]  fishes  draw  a 
larger  part  of  their  food  than  from  any  other  single  group.  In  fact, 
nearly  a  fifth  of  the  entire  amount  of  food  consumed  by  all. the  adult 
fishes  examined  by  me  consisted  of  aquatic  larvae  of  this  order,  the  great- 
er part  of  them  larvae  of  day  flies  (Ephemeridae), principally  of  the  genus 
Hexagenia.  These  neuropterous  larvae  were  eaten  especially  by  the 
miller's  thumb,  the  sheepshead,  the  white  and  striped  bass,  the  common 
perch,  thirteen  species  of  the  darters,  both  the  black  bass,  seven  of  the 
sunfishes,  the  rock  bass  and  the  croppies,  the  pirate  perch,  the  brook 
silversides,  the  sticklebacks,  the  mud  minnow,  the  top  minnows,  the 
gizzard  shad,  the  toothed  herring,  twelve  species  each  of  the  true 
minnow  family  and  of  the  suckers  and  buffalo,  five  catfishes,  the  dog- 


INSECTS   IN    RELATION   TO    OTHER   ANIMALS  239 

fish,  and  the  shovel  fish, — seventy  species  out  of  the  eighty-seven  which 
I  have  studied. 

"Among  the  above,  I  found  them  the  most  important  food  of  the 
white  bass,  the  toothed  herring,  the  shovel  fish  (fifty-one  per  cent.),  and 
the  croppies;  while  they  made  a  fourth  or  more  of  the  alimentary  con- 
tents of  the  sheepshead  (forty-six  per  cent.),  the  darters,  the  pirate 
perch,  the  common  sunfishes  (Lepomis  and  Chanohryltus) ,  the  rock 
bass,  the  little  pickerel,  and  the  common  sucker  (thirty-six  per 
cent.). 

"Ephemerid  larvae  were  eaten  by  two  hundred  and  thirteen  speci- 
mens of  forty-eight  species— not  counting  young.  The  larva  of  Hexa- 
genia,  one  of  the  commonest  of  the  'river  flies,'  was  by  far  the  most 
important  insect  of  this  group,  this  alone  amounting  to  about  half  of 
all  the  Neuroptera  eaten.  It  made  nearly  one  half  of  the  food  of  the 
shovel  fish,  more  than  one  tenth  that  of  the  sunfishes,  and  the  princi- 
pal food  resource  of  half-grown  sheepshead;  but  was  rarely  taken  by 
the  sucker  family,  and  made  only  five  per  cent,  of  the  food  of  the  catfish 
group. 

"The  various  larvae  of  the  dragon  flies,  on  the  other  hand,  were  much 
less  frequently  encountered.  They  seemed  to  be  most  abundant  in 
the  food  of  the  grass  pickerel  (twenty-five  per  cent.)  and  next  to  that, 
in  the  croppie,  the  pirate  perch,  and  the  common  perch  (ten  to  thirteen 
percent.). 

"Case-worms  (Phryganeidae)  were  somewhat  rarely  found,  rising  to 
fifteen  per  cent,  in  the  rock  bass  and  twelve  per  cent,  in  the  minnows  of 
the  Hybopsis  group,  but  otherwise  averaging  from  one  to  six  per  cent, 
in  less  than  half  of  the  species." 

Insects  in  Relation  to  Birds. — From  an  economic  point  of  view  the 
relations  between  birds  and  insects  are  extremely  important,  and  from 
a  purely  scientific  standpoint  they  are  no  less  important,  involving  as 
they  do  biological  interactions  of  remarkable  complexity. 

The  prevalent  popular  opinion  that  birds  in  general  are  of  inesti- 
mable value  as  destroyers  of  noxious  insects  is  a  correct  one,  as  Dr. 
Forbes  proved,  from  his  precise  and  extensive  studies  upon  the  food  of 
Ilhnois  birds,  involving  a  laborious  and  difficult  examination  of  the 
stomach  contents  of  many  hundred  specimens.  All  that  follows  is 
taken  from  Forbes,  when  no  other  author's  name  is  mentioned,  and 
though  the  percentages  given  by  him  apply  to  particular  years  and  would 
undoubtedly  vary  more  or  less  from  year  to  year,  they  are  here  for  con- 
venience regarded  as  representative  of  any  year  and  are  spoken  of  in 


240  ENTOMOLOGY 

the  present  tense.  About  two  thirds  of  the  food  of  birds  consists  of 
insects. 

Robin. — The  food  of  the  robin  in  Ilhnois,  from  February  to  May  in- 
clusive, consists  almost  entirely  of  insects;  at  first,  larvae  of  Bibio  albi- 
pennis  for  the  most  part,  and  then  caterpillars  and  various  beetles.  When 
the  small  fruits  appear,  these  are  largely  eaten  instead  of  insects;  thus 
in  June,  cherries  and  raspberries  form  fifty-five  per  cent,  and  insects 
(ants,  caterpillars,  wireworms  and  Carabidae)  forty-two  per  cent,  of  the 
food;  and  in  July,  raspberries,  blackberries  and  currants  form  seventy- 
nine  per  cent,  and  insects  (mostly  caterpillars,  beetles  and  crickets)  but 
twenty  per  cent,  of  the  food.  In  August,  insects  rise  to  forty-three  per 
cent,  and  fruits  drop  to  fifty-six  per  cent.,  and  these  are  mostly  cherries, 
of  which  two  thirds  are  wild  kinds.  In  September,  ants  form  fifteen 
per  cent,  of  the  food,  caterpillars  five  per  cent,  and  fruits  (mostly  grapes, 
mountain-ash  berries  and  moonseed  berries)  seventy  per  cent.  In 
October,  the  food  consists  chiefly  of  wild  grapes  (fifty- three  per  cent.), 
ants  (thirty-five  per  cent.),  and  caterpillars  (six  per  cent.). 

For  the  year,  judging  from  the  stomach  contents  of  one  hundred  and 
fourteen  birds,  garden  fruits  form  only  twenty-nine  per  cent,  of  the  food 
of  the  robin,  while  insects  constitute  two  thirds  of  the  food.  The  results 
are  confirmed  by  those  of  Professor  Beal  in  Michigan,  who  found  that 
more  than  forty-two  per  cent,  of  the  food  of  the  robin  consists  of  insects 
with  some  other  animal  matter,  the  remainder  being  made  up  of  various 
small  fruits,  but  notably  the  wild  kinds. 

Upon  the  whole,  the  robin  deserves  to  be  protected  as  an  energetic 
destroyer  of  cutworms,  white  grubs  and  other  injurious  insects,  and  the 
comparatively  few  cultivated  berries  that  the  bird  appropriates  are 
ordinarily  but  a  meagre  compensation  for  the  valuable  services  rendered 
to  man  by  this  familiar  bird. 

Catbird. — Not  so  much  can  be  said  for  the  catbird,  however,  for, 
though  its  food  habits  are  similar  to  those  of  the  robin,  it  arrives  later 
and  departs  earher,  with  the  result  that  it  is  less  dependent  than  the 
robin  upon  insects  and  that  berries  form  a  larger  percentage  of  its 
total  food. 

In  May,  eighty-three  per  cent,  of  the  food  of  the  catbird  consists  of 
insects,  mostly  beetles  (Carabidae,  Rhynchophora,  etc.),  crane-flies, 
ants  and  caterpillars  (Noctuidae) ;  while  dry  sumach  berries  are  eaten  to 
the  extent  of  seven  per  cent.  For  the  first  half  of  June,  the  record  is 
much  the  same,  with  an  increase,  however,  in  the  number  of  May 


INSECTS    IN    RELATION    TO    OTHER    ANIMALS  24I 

beetles  eaten;  in  the  second  half  of  the  month  the  food  consists  chiefly 
of  small  fruits,  especially  raspberries,  cherries  and  currants;  so  that  for 
the  month  as  a  whole,  only  forty-nine  per  cent,  of  the  food  is  made  up 
of  insects.  This  falls  to  eighteen  per  cent,  in  July,  when  three  quarters 
6f  the  food  consists  of  small  fruits,  mostly  blackberries,  however.  In 
August,  with  the  diminution  of  the  smaller  cultivated  fruits,  the  per- 
centage of  insects  rises  to  forty-six  per  cent.,  nearly  one  half  of  which  is 
made  up  of  ants  and  the  rest  of  caterpillars,  grasshoppers,  Hemiptera, 
Coleoptera,  etc.  In  September,  with  the  appearance  of  wild  cherries, 
elderberries,  Virginia  creeper  berries  and  grapes,  these  are  eaten  to  the 
extent  of  seventy-six  per  cent.,  the  insect  element  of  the  food  falling  to 
twenty-one  per  cent.,  of  which  almost  half  consists  of  ants,  and  the 
remainder  of  beetles  and  a  few  caterpillars. 

For  the  entire  year,  as  appears  from  the  study  of  seventy  specimens 
by  Forbes,  insects  form  forty-three  per  cent,  of  the  food  of  the  catbird 
and  fruits  fifty-two  per  cent.  As  the  injurious  insects  killed  are  offset 
by  the  beneficial  ones  destroyed,  "the  injury  done  in  the  fruit-garden  by 
these  birds  remains  without  compensation  unless  we  shall  find  it  in  the 
food  of  the  young,"  says  Professor  Forbes.  And  this  has  been  found,  to 
the  credit  of  the  catbird;  for  Weed  learned  that  the  food  of  three  nest- 
lings consisted  of  insects,  sixty-two  per  cent,  of  which  were  cutworms 
and  four  per  cent,  grasshoppers;  while  Judd  found  that  fourteen  nest- 
lings had  eaten  but  four  per  cent,  of  fruit,  the  diet  being  chiefly  ants, 
beetles,  caterpillars,  spiders  and  grasshoppers.  In  fact,  Weed  believes 
that,  on  the  whole,  the  benefit  received  from  the  catbird  is  much  greater 
than  the  harm  done,  and  that  its  destruction  should  never  be  permitted 
except  when  necessary  in  order  to  save  precious  crops. 

Bluebird. — The  excellent  reputation  which  the  bluebird  bears  every- 
where as  an  enemy  of  noxious  insects  is  well  deserved.  From  a  study  of 
one  hundred  and  eight  Illinois  specimens,  Forbes  finds  that  seventy- 
eight  per  cent,  of  the  food  for  the  year  consists  of  insects,  eight  per  cent, 
of  Arachnida,  one  per  cent,  of  Julidse  and  only  thirteen  per  cent,  of 
vegetable  matter,  edible  fruits  forming  merely  one  per  cent,  of  the  entire 
food.  The  insects  eaten  are  mostly  caterpillars  (chiefly  cutworms), 
Orthoptera  (grasshoppers  and  crickets)  and  Coleoptera  (Carabidae  and 
Scarabaeidae) .  Though  some  of  the  insects  are  more  or  less  beneficial  to 
man,  such  as  Carabidae  and  Ichneumonidae  (respectively  predaceous  and 
parasitic),  the  beneficial  elements  form  only  twenty-two  per  cent,  of  the 
food  for  the  year,  as  against  forty-nine  percent,  of  injurious  elements,  the 
remaining  twenty- nine  per  cent,  consisting  of  neutral  elements.    The  food 


242  »  ENTOMOLOGY 

of  the  nestlings,  according  to  Judd,  is  essentially  like  that  of  the  adults, 
being  "beetles,  caterpillars,  grasshoppers,  spiders  and  a  few  snails." 

Other  Insectivorous  Birds. — Weed  and  Dearborn,  from  whose 
excellent  work  the  following  notes  are  taken,  find  that  the  common 
chickadee  devours  immense  numbers  of  canker  worms,  and  that  more 
than  half  its  food  during  winter  consists  of  insects,  largely  in  the  form  of 
eggs,  including  those  of  the  common  tent  caterpillar  (C.  americana), 
the  fall  webworm  {H.  cunea)  and  particularly  plant  lice,  whose  eggs, 
small  as  they  are,  form  more  than  one  fifth  of  the  entire  food ;  more  than 
four  hundred  and  fifty  of  them  are  sometimes  eaten  by  a  single  bird  in 
one  day,  and  the  total  number  destroyed  annually  is  inconceivably 
large.  The  house  wren  is  almost  exclusively  insectivorous,  feeding 
upon  caterpillars  and  other  larvae,  ants,  grasshoppers,  gnats,  beetles, 
bugs,  spiders,  and  myriopods.  The  swallows,  also,  are  highly  insecti- 
vorous; ''most  of  their  food  is  captured  on  the  wing,  and  consists  of 
small  moths,  two-winged  flies,  especially  crane  flies,  beetles  in  great 
variety,  flying  bugs,  and  occasionally  small  dragon  flies.  The  young 
are  fed  with  insects."  Ninety  per  cent,  of  the  food  of  the  kingbird 
"consists  of  insects,  including  such  noxious  species  as  May  beetles, 
click-beetles,  wheat  and  fruit  weevils,  grasshoppers,  and  leafhoppers." 
The  honey  bees  eaten  by  this  bird  are  insignificant  in  number.  Wood- 
peckers destroy  immense  numbers  of  wood-boring  larvae,  bark-insects, 
ants,  caterpillars,  etc.  The  cuckoos  "are  unique  in  having  a  taste  for 
insects  that  other  birds  reject.  Most  birds  are  ready  to  devour  a  smooth 
caterpillar  that  comes  their  way,  but  they  leave  the  hairy  varieties 
severely  alone.  The  cuckoos,  however,  make  a  specialty  of  devouring 
such  unpalatable  creatures;  even  stink  bugs  and  the  poisonous  spiny 
larvae  of  the  lo  moth  are  freely  taken."  Caterpillars  form  fifty  per 
cent,  of  the  food  for  the  year;  Orthoptera  (grasshoppers,  katydids,  and 
tree  crickets),  thirty  per  cent.;  Coleoptera  and  Hemiptera,  six  per  cent, 
each;  and  flies  and  ants  are  taken  in  small  quantities.  "The  nestling 
birds  are  fed  chiefly  with  smooth  caterpillars  and  grasshoppers,  their 
stomachs  probably  being  unable  to  endure  the  hairy  caterpillars.  All 
in  all,  the  cuckoos  are  of  the  highest  economic  value.  They  do  no 
harm  and  accomplish  great  good.  If  the  orchardist  could  colonize 
his  orchards  with  them,  he  would  escape  much  loss."  The  quail  feeds 
largely  upon  insects  during  the  summer,  frequently  eating  the  Colorado 
potato  beetle  and  the  army  worm;  the  prairie  hen  has  similar  food 
habits  but  lives  almost  exclusively  on  grasshoppers,  when  these  are 
abundant. 


INSECTS    IN   RELATION   TO    OTHER   ANIMALS  243 

The  Insect  Food  of  Birds. — ''There  are  few  groups  of  injurious 
insects  that  enter  so  largely  into  the  composition  of  the  food  of  birds  as 
do  the  locusts,  or  short-horned  grasshoppers,  of  the  family  Acridiidce 
[now  Locustidajj.  The  enormous  destructive  power  of  these  insects 
is  well  known,  but  our  indebtedness  to  birds  in  checking  their  oscilla- 
tions is  less  generally  recognized."  Professor  Aughey,  who  has  made 
extensive  studies  upon  the  relation  of  birds  to  the  Rocky  Mountain 
locust,  found  that  upon  one  occasion  6  robins  had  eaten  265  of  these 
insects,  5  catbirds  152,  3  blue-birds  67,  7  barn  swallows  139,  7  night 
hawks  348,  16  yellow-billed  cuckoos  416,  8  flickers  252,  8  screech  owls 
219,  and  I  humming  bird  4;  while  crows  and  blue-jays  had  eaten  large 
numbers  of  the  locusts;  and  grouse,  quail  and  prairie  hen,  enormous  num- 
bers. Even  shore  birds,  such  as  geese,  ducks,  gulls  and  pelicans  came  to 
share  in  the  feast.  Aughey  estimated  that  the  locusts  eaten  in  one  day 
by  the  passerine  birds  of  the  eastern  half  of  Nebraska  were  sufficient  to 
destroy  in  a  single  day  174,397  tons  of  crops,  valued  at  $1,743.97. 

Weed  and  Dearborn  state  that,  of  Hemiptera,  Jassidae  are  very  often 
found  in  the  stomachs  of  birds,  and  that  aphids  and  their  eggs  form  a 
large  part  of  the  food  of  many  of  the  smaller  birds,  such  as  the  warblers, 
nuthatches,  kinglets  and  chickadees.  A  large  proportion  of  the  cater- 
pillars of  the  Lepidoptera  are  eagerly  devoured  by  birds,  forming  an 
important  element  of  the  food  of  many  species.  The  hairy  caterpillars 
are  eaten  by  cuckoos  and  blue-jays  and  the  large  saturniid  caterpillars, 
such  as  cecropia  and  polyphemus,  by  some  of  the  hawks.  Almost  all 
kinds  of  Goleoptera  are  food  for  birds,  but  especially  the  grubs  of  Scara- 
baeidae,  which  are  eagerly  devoured  by  robins,  blackbirds,  crows  and 
other  birds.  Of  the  Diptera,  Itonididae  and  other  gnats  are  eaten 
by  swallows,  swifts  and  night  hawks;  while  crane  flies,  TipuHdae,  are 
often  found  in  the  stomachs  of  birds.  Among  Hymenoptera,  ants  are 
eaten  extensively  by  woodpeckers,  catbirds  and  many  other  species,  as 
are  also  Ichneumonidae  and  other  parasitic  forms — these  last  by  the 
flycatchers  in  particular. 

The  Regulative  Action  of  Birds  upon  Insect  Oscillations.^ The  worst 
injuries  by  insects  are  done  by  species  that  fluctuate  excessively  in 
number  as  the  result  of  variations  in  those  manifold  forces  that  act  as 
checks  upon  the  multiplication  of  the  species. 

In  order  to  determine  whether  birds  do  anything  to  reduce  existing 
oscillations  of  injurious  insects,  Professor  Forbes  made  studies  upon  the 
food  of  birds  which  were  shot  in  an  IlHnois  apple  orchard  which  was 
being  ravaged  by  canker-worms.     In  this  orchard,  birds  were  present  in 


244  ENTOMOLOGY 

extraordinary  number  and  variety,  there  being  at  least  thirty-five 
species-,  most  of  which  were  studied  by  Forbes,  from  whose  exhaustive 
tables  the  following  food-percentages  are  taken: 

Birds  Insects,      Canker-worms, 

Examined  Per  Cent.         Per  Cent. 

Robin 9  93  21 

Catbird 14  98  ^5 

Brown  Thrush 4  94  12 

Bluebird 5  9S  12 

Black-capped  Chickadee 2  100  61 

House  Wren 5  91  46 

Tennessee  Warbler i  100  80 

Summer  Yellow  Bird 5  94  67 

Black- throated  Green  Warbler i  100  7°      . 

Maryland  Yellow-throat 2  100  37 

Baltimore  Oriole 3  1°°  40 

To  quote  Forbes:  "Three  facts  stand  out  very  clearly  as  results  of 
these  investigations:  i.  Birds  of  the  most  varied  character  and  habits, 
migrant  and  resident,  of  all  sizes,  from,  the  tiny  wren  to  the  blue-jay, 
birds  of  the  forest,  garden  and  meadow,  those  of  arboreal  and  those  of 
terrestrial  habits,  were  certainly  either  attracted  or  detained  here  by  the 
bountiful  supply  of  insect  food,  and  were  feeding  freely  upon  the  species 
most  abundant.  That  thirty-five  per  cent,  of  the  food  of  all  the  birds 
congregated  in  this  orchard  should  have  consisted  of  a  single  species  of 
insect,  is  a  fact  so  extraordinary  that  its  meaning  can  not  be  mistaken. 
Whatever  power  the  birds  of  this  vicinity  possessed  as  checks  upon 
destructive  irruptions  of  insect  life  was  being  largely  exerted  here  to 
restore  the  broken  balance  of  organic  nature.  And  while  looking  for 
their  influence  over  one  insect  outbreak  we  stumbled  upon  at  least  two 
others,  less  marked,  perhaps  incipient,  but  evident  enough  to  express 
themselves  clearly  in  the  changed  food  ratios  of  the  birds. 

"2.  The  comparisons  made  show  plainly  that  the  reflex  efi'ect  of  this 
concentration  on  two  or  three  unusually  numerous  insects  was  so  widely 
distributed  over  the  ordinary  elements  of  their  food  that  no  especial 
chance  was  given  fcir  the  rise  of  new  fluctuations  among  the  species 
commonly  eaten.  That  is  to  say,  the  abnormal  pressure  put  upon  the 
cankerworm  and  vine-chafer  was  compensated  by  a  general  diminution 
of  the  ratios  of  all  the  other  elements,  and  not  by  a  neglect  of  one  or  two 
alone.  If  the  latter  had  been  the  case,  the  criticism  might  easily  have 
been  made  that  the  birds,  in  helping  to  reduce  one  oscillation,  were 
setting  others  on  foot. 

"3.  The  fact  that,  with  the  exception  of  the  indigo  bird,  the  species 


INSECTS    IN   RELATION   TO    OTHER    ANIMALS  245 

whose  records  in  the  orchard  were  compared  with  those  made  elsewhere 
had  eaten  in  the  former  situation  as  many  caterpillars  other  than  canker- 
worms  as  usual,  simply  adding  their  canker-worm  ratios  to  those  of  other 
caterpillars,  goes  to  show  that  these  insects  are  favorites  with  a  majority 
of  birds." 

The  Relations  of  Birds  to  Predaceous  and  Parasitic  Insects. — The 
false  assumption  is  often  made  that  a  bird  is  necessarily  inimical  to 
man's  interest  whenever  it  destroys  a  parasitic  or  a  predaceous  insect. 
Weed  and  Dearborn  attack  this  assumption  as  follows: 

"Suppose  an  ichneumon  parasite  is  found  in  the  stomach  of  a  robin 
or  other  bird:  it  may  belong  to  any  one  of  the  following  categories: 

"i.  The  primary  parasite  of  an  injurious  insect. 

"2.  The  secondary  parasite  of  an  injurious  insect. 

"3.  The  primary  parasite  of  an  insect  feeding  on  a  noxious  plant. 

"4.  The  secondary  parasite  of  an  insect  feeding  on  a  noxious  plant. 

"5.  The  primary  parasite  of  an  insect  feeding  on  a  wild  plant  of  no 
economic  value. 

"6.  The  secondary  parasite  of  an  insect  feeding  on  a  wild  plant  of  no 
economic  value. 

"j.  The  primary  parasite  of  a  predaceous  insect. 

"8.  The  primary  parasite  of  a  spider  or  a  spider's  egg. 

"This  hst  might  easily  be  extended  still  farther,  and  the  assumption 
that  the  parasite  belongs  to  the  first  of  these  categories  is  unwarranted 
by  the  facts  and  does  violence  to  the  probabilities  of  the  case. 

"A  correct  idea  of  the  economic  role  of  the  feathered  tribes  may  be 
obtained  only  by  a  broader  view  of  nature's  methods, — a  view  in  which 
we  must  ever  keep  before  the  mind's  eye  the  fact  that  all  the  parts  of 
the  organic  world,  from  monad  to  man,  are  linked  together  in  a  thousand 
ways,  the  net  result  being  that  unstable  equilibrium  commonly  called 
'the  balance  of  nature.'" 

The  general  subject  of  food  relations  and  interactions  of  insects  is 
taken  up  in  the  chapter  on  ecology  (page  373). 

Efficiency  of  Protective  Adaptations  of  Insects. — Interesting  from 
a  scientific  point  of  view  are  the  various  adaptations  by  means  of  which 
insects  are  protected  more  or  less  from  their  bird  enemies.  Colora- 
tional  adaptations  having  been  discussed  in  another  chapter,  there 
remain  for  consideration— (i)  hairs,  (2)  stings,  (3)  odors,  flavors  and 
irritants.  Most  of  what  follows  is  from  an  admirable  paper  by  Dr.  Judd, 
whose  data  are  based  upon  his  examination  of  the  stomach  contents  of 
fifteen  thousand  birds. 


246  ENTOMOLOGY 

Hairs. — "  Excepting  two  species  of  cuckoos,  no  species  of  bird  in  the 
eastern  United  States,  so  far  as  I  am  aware,  makes  a  business  of  feeding 
upon  hairy  caterpillars."  Judd  observed  that  the  fall  web  worm, 
Hyphantria  cunea,  infesting  a  pear  tree  was  not  at  all  molested,  in  spite 
of  the  fact  that  the  tree  was  tenanted  by  three  broods  of  birds  at  the 
time,  namely,  kingbirds,  orchard  orioles  and  English  sparrows.  The 
hairy  arctiid  caterpillars,  however,  are  eaten  by  a  few  birds :  the  robin, 
bluebird,  catbird,  sparrowhawk,  cuckoos  and  shrikes;  and  the  spiny 
larvae  of  Vanessa  antiopa  by  cuckoos  and  the  Baltimore  oriole;  while 
the  hairy  caterpillars  of  the  gipsy  moth  are  known  to  be  eaten  in  Massa- 
chusetts by  no  fewer  than  thirty-one  species  of  birds,  notably  cuckoos, 
Baltimore  oriole,  catbird,  chickadee,  blue- jay,  chipping  sparrow,  robin, 
vireos  and  the  crow,  these  birds  being  of  no  little  assistance  in  the  sup- 
pression of  this  pest.  These  are  exceptional  cases,  however,  and  in 
general  the  hairiness  of  caterpillars  appears  to  be  a  highly  effective 
protection  against  most  birds. 

Stings. — Some  birds  (chewink,  young  ducks)  are  fatally  affected  by 
eating  honey  bees.  The  blue-jays,  however,  will  eat  Bombus  (bumble- 
bees) and  Xylocopa,  and  flycatchers  and  swallows  feed  habitually  upon 
stinging  Hymenoptera,  particularly  Scoliidae,  while  a  great  many  birds 
eat  Myrmicidae,  or  stinging  ants.  The  formic  acid  of  ants  does  not 
protect  them  from  wholesale  destruction  by  birds;  Judd  found  three 
thousand  ants  in  the  stomach  of  a  flicker.  "Stingless  ants  pretend  to 
sting  but  many  birds  they  do  not  deceive."  The  stinging  caterpillar 
of  Automeris  io  is  occasionally  eaten  by  the  yellow-billed  cuckoo. 
Aside  from  these  exceptions,  the  stings  of  insects  are  an  extremely 
efficient  means  of  defence. 

Odors,  Flavors  and  Irritants. — The  malodorous  Heteroptera  in 
general  are  food  for  most  birds;  Lygus,  Reduviidae  (assassin  bugs)  and 
Pentatomidae  (stink  bugs)  are  eaten  by  song  sparrows,  and  £w5c/?w/w5  by 
blackbirds  and  crows.  The  odors  of  Heteroptera  are  by  no  means 
universally  protective. 

Among  Coleoptera,  the  showy,  ill-scented  or  ill-flavored  Coccinellidae 
(lady  beetles)  are  eaten  by  very  few  birds — the  flycatchers  and  swallows 
— and  are  refused  by  caged  blue-jays  and  song  sparrows  even  when 
these  birds  are  hungry.  Of  Chrysomehdae,  the  Colorado  potato  beetle 
is  refused  by  the  catbird,  blue-jay  and  song  sparrow,  and  Diabrotica 
is  not  often  eaten,  except  by  catbirds  and  thrushes.  "The  smaller 
Carabidae  (ground  beetles)  whether  stinking  or  not,  are  eaten  by 
practically  all  land  birds."     Crows,  blackbirds  and  jays  eagerly  swallow 


INSECTS    IN   RELATION    TO    OTHER   ANIMALS  247 

the  showy  Calosoma  scrutator,  and  the  first  two  birds  are  especially  fond 
of  Harpalus  caliginosus  and  H.  pennsylvanicus ,  and  feedGalerita  to  their 
young.  "A  score  of  smaller  Carabidae  (ground  beetles)  and  Chryso- 
melidae  (leaf  beetles)  metallic  and  conspicuously  colored,  are  habitually 
eaten  by  birds  that  have  an  abundance  of  other  insect  food  to  pick  from." 

The  stenches  of  Lampyrida?  (firefly  family)  appear  to  be  more  effec- 
tive than  those  of  Carabidae.  Telephorus  is  occasionally  eaten,  but  Pho- 
tinus  rarely  if  at  all.  Chauliognathus  is  not  eaten  by  many  birds 
(though  flycatchers  and  swallows  select  this  insect)  and  the  genus  is 
regarded  unfavorably  by  caged  catbirds  and  blue-jays. 

In  regard  to  other  insects,  Judd  finds  that  Epicauta  (blister  beetle) 
with  its  irritant  fluid,  is  immune  from  all  but  the  kingbird;  Cyllene 
seldom  occurs  in  the  stomachs  of  birds;  May  flies  and  caddis  flies, 
however,  are  terribly  persecuted,  but  swiftly  flying  Diptera  and  Odonata 
are  highly  immune. 

From  such  facts  as  these,  Judd  properly  infers,  "not  cases  of  protec- 
tion and  nori^protection,  but  cases  of  greater  and  lesser  efficiency  of 
protective  devices." 


CHAPTER  IX 

TRANSMISSION  OF  DISEASES  BY  INSECTS 

It  is  commonly  known  that  some  kinds  of  insects  are  of  vital  impor- 
tance to  man  as  agents  in  the  transmission  of  certain  diseases.  In 
recent  years  immense  progress  has  been  made  in  our  knowledge  of  insect- 
borne  diseases. 

Malaria 

So  far  as  is  known,  malaria  is  transmissible  only  through  the  agency 
of  mosquitoes. 

The  malaria  "germ,"  discovered  in  1880  by  the  French  army  surgeon 
Laveran,  may  be  found  as  a  pale,  amoeboid  organism  {Laverania, 
Fig.  273)  in  the  red  blood  corpuscles  of  persons  afflicted  with  the  disease. 
This  organism  {schizont,  2)  grows  at  the  expense  of  the  haemoglobin  of 
the  corpuscle  (3-5)  and  its  growth  is  accompanied  by.  an  increasing 
deposit  of  black  granules  (melanin),  which  are  doubtless  excretory  in 
their  nature.  At  length,  the  amoebula  divides  into  many  spores  (mero- 
zoites,  6)  which  by  the  disintegration  of  the  corpuscle  are  set  free  in  the 
plasma  of  the  blood.  Here  many  if  not  most  of  the  spores,  and  the 
pigment  granules  as  well,  are  attacked  and  absorbed  by  leucocytes,  or 
white  blood  corpuscles,  while  some  of  the  spores  may  invade  healthy  red 
corpuscles  and  develop  as  before.  The  period  of  sporulation,  as  Golgi 
found,  is  coincident  with  that  of  the  "chill"  experienced  by  the  patient; 
and  quinine  is  most  effective  when  administered  just  before  the  sporula- 
tion period.  The  destruction  of  red  blood  corpuscles  explains  the  pallid, 
or  ancemic,  condition  which  is  characteristic  of  malarial  patients.  In 
three  or  four  days  the  number  of  red  corpuscles  may  be  reduced  from 
5,000,000  per  cubic  millimeter — the  normal  number — to  3,000,000;  and 
in  three  or  four  weeks  of  intermittent  fever,  even  to  1,000,000. 

Authorities  recognize  at  least  three  species  of  malaria  parasites 
affecting  man:  (i)  the  tertian  (Plasmodium  vivax),  with  an  asexual  cycle 
of  forty-eight  hours,  causing  the  fever  to  recur  every  two  days;  (2) 
the  quartan  (P.  malarice),  with  a  cycle  of  sbventy-two  hours,  causing 
fever  every  third  day;  and  (3)  the  suhtertian  or  malignant  form  (Laver- 
ania falciparum)  of  which  there  are  three  varieties  (perhaps  species) , 
with  cycles  of  twenty-four  or  forty-eight  hours,  according  to  the  variety. 

248 


Pig.  273. — Life  history  of  malaria  parasite,  Lai'drawja/a/ci^arMTW.  i,  sporozoite,  intro- 
duced by  mosquito  into  human  blood;  the  sporozoite  becomes  a  schizont.  2,  young  schi- 
zont,  which  enters  a  red  blood  corpuscle.  3,  young  schizont  in  a  red  blood  corpuscle.  4, 
full-grown  schizont,  containing  numerous  granules  of  melanin.  5,  nuclear  division  prei)ara- 
tory  to  sporulation.  6,  spores,  or  merozoites,  derived  from  a  single  mother-cell.  7,  young 
macrogametocyte  (female),  derived  from  a  merozoite  and  situated  in  a  red  blood  corpuscle. 
7a,  young  microgametocyte  (male)  derived  from  a  merozoite.  8,  full-grown  macrogameto- 
cyte. 8a,  full-grown  microgametocyte.  In  stages  8  and  8a  the  parasite  is  taken  into  the 
stomach  of  a  mosquito;  or  else  remains  in  the  human  blood.  9,  mature  macrogamete, 
capable  of  fertilization;  the  round  black  extruded  object  may  probably  be  termed  a  "polar 
body."  9a,  mature  microgametocyte,  preparatory  to  forming  microgametes.  96,  resting 
cell,  bearing  six  flagellate  microgametes  (male).  10,  fertilization  of  a  macrogamete  by  a 
motile  microgamete.  The  macrogamete  next  becomes  an  ookinete.  11,  ookinete,  or 
wandering  cell,  which  penetrates  into  the  wall  of  the  stomach  of  the  mosquito.  12, 
ookinete  in  the  outer  region  of  the  wall  of  the  stomach,  i.e.,  next  to  the  body  cavity.  13, 
young  oocyst,  derived  from  the  ookinete.  14,  oocyst,  containing  sporoblasts,  which  are  to 
develop  into  sporozoites.  15,  older  oocyst.  16,  mature  oocyst,  containing  sporozoites, 
which  are  liberated  into  the  body  cavity  of  the  mosquito  and  carried  along  in  the  blood 
of  the  insect.  17,  transverse  section  of  salivary  gland  of  an  Anopheles  mosquito,  showing 
sporozoites  of  the  malaria  parasite  in  the  gland  cells  surrounding  the  central  canal. 

1-6  illustrate  schizogony  (asexual  production  of  spores);  7-16,  sporogony  (sexual  pro- 
duction of  spores). 

After  Grassi  and  Leuckart,  by  permission  of  Dr.  Carl  Chun. 

249 


250  ENTOMOLOGY 

Two  or  more  sets  of  parasites  in  the  human  blood,  sporulating  at 
different  times,  may  cause  the  fever  to  recur  at  intervals  that  are 
apparently  irregular. 

After  several  successive  asexual  generations,  there  are  produced 
merozoites  which  develop — no  longer  into  schizonts — but  into  sexual 
forms,  or  gavietes.  These  occur  in  red  blood  corpuscles  either  as 
macrogametocytes  (female,  7,  8)  or  as  microgametocytes  (male,  7a,  8a), 
in  which  forms  the  parasite  is  introduced  into  the  stomach  of  a  mosquito 
which  has  been  feeding  upon  the  blood  of  a  malarial  patient.  The 
macrogametocyte  now  leaves  its  blood  corpuscle  and  becomes  a  spherical 
macrogamete  (9) ;  and  the  microgametocyte  also  becomes  spherical 
{ga) ;  but  the  latter  puts  forth  a  definite  number  {six,  in  L.  falciparum, 
gb)  of  flagella,  or  microgametes,  which  separate  off  as  motile  male  bodies, 
capable  of  fertihzing  the  macrogametes.  A  microgamete  penetrates  a 
macrogamete  (10)  and  the  nucleus  of  the  one  unites  with  that  of  the 
other.  The  fertilized  macrogamete,  or  zygote,  now  becomes  a  migrating 
cell,  or  ookinete  (11),  which  penetrates  almost  through  the  wall  of  the 
stomach  of  the  mosquito  (12)  and  then  becomes  a  resting  cell,  or  cyst. 
This  oocyst  (13)  grows  rapidly  and  its  contents  develop,  by  direct  nuclear 
division,  into  sporohlasts  (14,  15),  which  differentiate  into  spindle- 
shaped  sporozoites  (16,  17).  The  sporozoites  are  liberated  into  the 
body  cavity  of  the  mosquito,  carried  in  the  blood  to  the  salivary  glands 
(as  well  as  elsewhere)  and  thence  along  the  hypopharynx  into  the 
body  of  a  human  being,  bird  or  other  animal  attacked  by  the 
insect. 

The  role  of  the  mosquito  as  the  intermediary  host  of  malarial  organ- 
isms was  discovered  by  Manson  and  Ross  and  confirmed  by  Koch,  Stern- 
berg and  others.  It  has  been  found  repeatedly  that  certain  mosquitoes 
(Anopheles)  after  feeding  on  the  blood  of  a  malarial  patient  can  transmit 
the  disease  by  means  of  their  "bites"  to  healthy  persons.  Thus, 
Anopheles  mosquitoes  were  fed  on  the  blood  of  malarial  subjects  in 
Rome  and  then  sent  to  London,  where  a  son  of  Dr.  Manson  allowed  him- 
self to  be  bitten  by  the  insects.  Though  previously  free  from  the 
malarial  organism,  he  contracted  a  well-marked  infection  as  the  result 
of  the  inoculation. 

Furthermore,  it  is  highly  probable  that  malaria  cannot  be  trans- 
mitted to  man  except  through  the  agency  of  the  mosquito.  This  ap- 
pears from  the  oft-cited  experiment  of  Doctors  Sambon  and  Low  on  the 
Roman  Campagna,  a  place  notorious  for  malaria.  There  the  experi- 
menters lived  during  the  malarial  season  of  1900,  freely  exposed  to  the 


TRANSMISSION    OF   DISEASES   BY   INSECTS  25 1 

emanations  from  the  marsh  and  taking  no  precautions  except  to  screen 
their  house  carefully  against  mosquitoes  and  to  retire  indoors  before 
the  insects  appeared  in  the  evening.  Simply  by  excluding  Anopheles 
mosquitoes,  with  which  the  Campagna  swarmed,  these  investigators 
remained  perfectly  immune  from  the  malaria  which  was  ravaging  the 
vicinity. 

In  a  later  experiment  on  the  island  of  Formosa,  one  company  of 
Japanese  soldiers  was  protected  from  mosquitoes  and  suffered  no 
malaria,  while  a  second  and  unprotected  company  contracted  the 
disease. 

The  evident  preventive  measures  to  be  taken  against  malaria  are 
(i)  the  avoida;nce  of  mosquito  bites,  by  means  of  screens,  and  washes  of 
eucalyptus  oil,  camphor,  oil  of  pennyroyal,  oil  of  tar,  etc.,  appHed  to 
exposed  parts  of  the  body;  (2)  the  isolation  of  malarial  patients  from 
mosquitoes,  in  order  to  prevent  infection;  (3)  the  destruction  of  mosqui- 
toes in  their  breeding  places,  especially  by  the  use  of  kerosene  and  by 
drainage.  During  unavoidable  exposure  in  malarious  regions,  quinine 
should  be  taken  in  doses  of  six  to  ten  grains  during  the  day  at  intervals 
of  four  or  five  days  (Sternberg) . 

In  Macedonia  in  191 6  there  were  some  800,000  cases  of  malaria, 
with  2,000  deaths  in  the  French  and  AlHed  army.  Where  the  disease 
was  most  severe  Anopheles  mosquitoes  were  present  in  enormous  num- 
bers. A  striking  peculiarity  of  this  epidemic  was  the  marked  failure 
of  quinine  as  a  preventive  or  remedy.  This  failure  was  explained  as 
being  due  to  the  development  of  quinine-resistant  strains  of  the  malaria 
parasites. 

Culex  and  Anopheles.^ — More  than  five  hundred  species  of  mosqui- 
toes have  been  described.  Of  these  only  the  genus  Anopheles  transrhits 
malaria  to  man;  though  in  India,  Ross  found  that  Culex  transmits  a 
form  of  malaria  to  sparrows.  These  two  common  genera  are  easily 
distinguishable.  In  Culex  the  wings  are  clear;  in  Anopheles  they  are 
spotted  with  brown.  In  Culex  when  resting,  the  axis  of  the  body 
forms  a  curved  line,  the  insect  presenting  a  hump-backed  appearance; 
in  Anopheles  the  axis  forms  a  straight  line.  Culex  has  short  maxillary 
palpi,  while  in  Anopheles  they  are  almost  as  long  as  the  proboscis.  The 
note  of  the  iemale  Anopheles  is  several  tones  lower  than  that  of  Culex, 
and  only  the  female  is  bloodthirsty,  by  the  way.  As  regards  eggs, 
larvae  and  pupae,  the  two  genera  differ  greatly.  The  eggs  of  Culex  are 
laid  in  a  mass  and  those  of  Anopheles  singly;  the  larvae  of  Culex  hang 
from  the  surface  film  of  a  pool  at  an  angle  of  about  forty-five  degrees, 


252  ENTOMOLOGY 

while  those  of  Anopheles  are  almost  parallel  with  the  surface  of  the 
water  in  which  they  Uve. 

The  bite  of  an  Anopheles  is  not  necessarily  injurious,  of  course,  unless 
the  insect  has  had  recent  access  to  a  malarious  person.  Anopheles  may 
be  present  where  there  is  no  malaria.  On  the  other  hand,  it  has  been 
found  impossible  to  prove  that  malaria  exists  where  there  are  no  Anoph- 
eles mosquitoes.  Finally,  fevers  are  sometimes  diagnosed  as  malarial 
which  are  not  so. 

Possibly  the  malarial  parasite  can  complete  its  cycle  of  development 
in  other  animals  than  man.  It  is  also  possible  that  originally  the  mala- 
rial organism  was  derived  by  mosquitoes  from  the  stems  or  other  parts 
of  aquatic  plants,  and  that  its  effects  on  man  are  incidental  phenomena. 

Yellow  Fever 

From  1793  to  1900  there  occurred  in  the  United  States  not  less  than 
half  a  million  cases  of  yellow  fever  and  one  hundred  thousand  deaths 
from  the  disease.  New  Orleans  suffered  the  worst  with  more  than  forty- 
one  thousand  deaths,  followed  by  Philadelphia  with  ten  thousand  and 
Memphis  with  almost  eight  thousand;  while  Charleston,  New  York 
City  and  Norfolk,  Virginia,  lost  together  more  than  ten  thousand  lives. 

The  enormous  financial  loss  from  all  the  epidemics  of  yellow  fever  is 
beyond  exact  computation;  the  epidemic  of  1878  cost  New  Orleans  more 
than  ten  million  dollars. 

Yellow  fever  is  now  within  human  control ;  with  no  thanks  to  those 
who  at  first  violently  opposed  the  theory,  and  later  denied  the  fact,  of 
its  transmission  by  mosquitoes. 

Until  1 901  yellow  fever  was  fought  energetically,  but  fought  in  the 
dark.  An  immense  amount  of  energy  was  misdirected  and  millions  of 
dollars  wasted  in  the  fight.  On  the  supposition  that  bacteria  were  the 
cause  of  the  disease,  methods  of  quarantine,  burning  and  fumigation 
were  employed  that  destroyed  an  enormous  amount  of  property  includ- 
ing valuable  cargoes,  and  paralyzed  the  business  and  social  activities  of 
great  cities. 

Official  accounts  of  yellow  fever  published  before  1900  often  describe 
the  disease  as  being  due  to  some  insidious  poison  borne  by  the  air  and 
introduced  into  the  human  body,  probably  through  the  respiratory 
system.  It  was  observed  that  the  disease  was  often  conveyed  down 
the  wind,  that  it  was  not  carried  far  from  the  nearest  focus  of  infection, 
that  infection  was  less  liable  to  occur  in  daylight  than  by  night,  and 


TRANSMISSION    OF   DISEASES   BY   INSECTS  253 

that  cases  arose  on  shore  when  the  only  source  of  infection  was  a  ship 
that  had  not  yet  touched  the  land.  These  facts  and  many  others 
which  formerly  involved  the  disease  in  mystery,  are  now  quite  intelli- 
gible in  the  hght  of  the  mosquito- theory  of  transmission. 

Finlay's  Work. — The  pioneer  work  leading  toward  the  control  of 
yellow  fever  was  done  by  Dr.  Charles  J.  Finlay,  of  Havana,  Cuba,  who 
not  only  advocated  the  mosquito-theory  strongly  for  many  years,  but 
also  inoculated  by  means  of  mosquitoes  ninety  human  subjects,  some 
of  whom  came  down  with  what  he  believed  to  be  a  mild  form  of  yellow 
fever.  His  valuable  work  prepared  the  way  for  the  briUiant  investi- 
gations of  Major  Reed  and  his  associates. 

United  States  Yellow  Fever  Commission. — Major  Walter  Reed 
was  president  of  the  board  of  medical  ofhcers  sent  to  Cuba  in  June,  1900, 
to  study  the  acute  infectious  diseases  of  the  island;  his  associates  were 
James  Carroll,  Jesse  W.  Lazear  and  A.  Agramonte. 

At  that  time  Sanarelli's  theory  as  to  the  bacillary  causation  of  yellow 
fever  was  in  favor,  though  Reed  and  Carroll  has  already  shown  that  the 
bacillus  of  Sanarelli  bore  no  special  relation  to  the  disease.  After  further 
investigations  on  this  subject  in  Cuba,  with  negative  results,  the  com- 
mission "concluded  to  test  the  theory  of  Finlay,"  in  Dr.  Reed's  words. 
For  this  purpose  General  Leonard  Wood,  the  mihtary  governor  of  Cuba, 
gave  permission  for  experiments  on  human  beings  and  granted  a  liberal 
sum  of  money  for  the  reward  of  volunteer  subjects. 

The  commission  succeeded  in  demonstrating  how  yellow  fever  is 
transmitted;  after  that  the  methods  of  prevention  to  be  employed  were 
evident. 

The  experiments,  planned  and  directed  by  Major  Reed,  are  models 
of  their  kind.  All  possible  sources  of  error  were  excluded;  hence  there 
was  no  uncertainty  in  the  interpretation  of  the  results,  the  accuracy  of 
which  has  been  confirmed  by  subsequent  commissions  and  by  many 
independent  investigators. 

In  the  value  of  his  services  Major  Walter  Reed  ranks  among  the 
greatest  benefactors  of  mankind.  Before  his  death,  which  occurred  in 
1902,  he  received  great  honors  for  his  brilliant  achievements. 

Experiments  in  Cuba. — For  experimental  purposes  Major  Reed  es- 
tablished a  camp  about  four  miles  from  Havana.  To  prevent  the 
introduction  of  the  fever  from  the  outside  the  inmates  of  the  camp  were 
rigidly  quarantined;  non-immunes  were  confined  to  the  camp  or,  if  re- 
leased, not  allowed  to  return.  In  order  that  the  study  of  yellow  fever 
might  not  be  complicated  by  the  presence  of  any  other  disease,  a  com- 


2  54  ENTOMOLOGY 

plete  record  was  kept  of  the  health  of  every  subject;  furthermore,  ample 
time  was  allowed  for  any  possible  development  of  the  disease  within  the 
camp  before  the  experiments  were  begun.  In  short,  the  precautions 
taken  were  so  thorough  that  yellow  fever  never  appeared  in  the  camp 
except  at  the  will  of  the  experimenters. 

Harmlessness  of  Fomites. — In  a  specially  constructed  building, 
which  was  screened  against  mosquitoes  and  purposely  ill-ventilated, 
volunteers  slept  for  twenty  nights  with  bedding  and  clothing  that  had 
been  contaminated  by  yellow  fever  patients,  and  tried  in  every  other 
way  to  contract  the  disease,  if  possible,  from  the  fomites,  or  belongings, 
of  fever  subjects;  yet  the  health  of  these  volunteers  remained  unimpaired; 
though  they  were  not  immunes,  for  some  of  them  were  subsequently 
infected  artificially  by  means  of  mosquitoes. 

Transmission  by  Transfusion. — It  was  found  that  the  disease  could 
be  conveyed  to  non-immunes  by  the  subcutaneous  injection  of  blood 
taken  from  the  veins  of  patients  during  the  first  three  days  of  the  disease. 

Experiments  with  Mosquitoes. — These  experiments  were  made  at 
a  time  of  the  year  when  there  was  the  least  chance  of  acquiring  the  dis- 
ease naturally.  The  mosquitoes  used  were  bred  from  the  eggs  and  kept 
active  by  being  maintained  at  a  summer  temperature.  From  time  to 
time  some  of  them  were  taken  away  to  a  yellow  fever  hospital,  fed  on  the 
blood  of  patients  and  applied  to  non-immunes  in  the  camp  at  varying 
intervals  from  the  time  of  feeding.  The  occupants  of  the  camp  were,  of 
course,  protected  carefully  from  accidental  mosquito  bites.  When  a 
subject  came  down  with  yellow  fever  as  the  result  of  an  experimental 
inoculation  he  was  at  once  removed  from  the  camp  to  a  yellow  fever 
hospital. 

In  a  mosquito-proof  building  a  single  room  was  divided  into  two 
compartments  simply  by  means  of  a  partition  of  wire  netting.  On  one 
side  of  the  screen  infected  mosquitoes  were  liberated;  and  a  brave  non- 
immune, who  had  been  in  quarantine  for  thirty-two  days,  entered  the 
compartment,  allowed  himself  to  be  bitten  several  times,  and  contracted 
the  disease.  In  the  opposite  compartment,  free  from  mosquitoes,  non- 
immunes slept  with  perfect  safety ;  and  the  other  room  became  harmless 
as  soon  as  the  mosquitoes  were  removed. 

In  another  experiment  the  subject  acquired  the  disease  by  thrusting 
his  arm  into  a  jar  of  infected  mosquitoes.  Eighteen  non-immunes  were 
inoculated,  ten  of  them  successfully.  It  was  demonstrated  that  yellow 
fever  is  transmitted  by  the  bite  of  a  mosquito,  and  in  no  other  way 
except  by  the  artificial  injection  of  diseased  blood.     The  mosquito  can 


TRANSMISSION    OF    DISEASES   BY    INSECTS 


255 


obtain  infected  blood  from  a  patient  during  only  the  first  three  days  of 
his  disease;  in  other  words,  the  patient  is  no  longer  a  menace  to  other 
persons  after  three  days  from  the  time  when  he  comes  down  with  yellow 
fever,  which  is  from  three  to  six  days  after  the  bite. 

After  biting  a  patient  the  mosquito  cannot  convey  the  infection  until 
at  least  twelve  days  have  elapsed;  thereafter  it  can  transmit  the  disease 
for  certainly  six  weeks  and  possibly  eight  weeks. 

Dr.  James  Carroll  allowed  himself  to  be  bitten  by  an  infected  mos- 
quito and  consequently  suffered  a  severe  attack  of  yellow  fever.  He 
recovered  from  this,  but  was  left  with  an  affection  of  the  heart  from 
which  he  died  in  1907. 

Dr.  Lazear  failed  to  acquire  the  disease  artificially,  early  in  the 
course  of  the  experiments;  but  a  little  later,  while  visiting  yellow  fever 
patients  in  a  hospital,  was  bitten  by  a  mosquito  which  he  deliberately 
allowed  to  remain  on  his  hand.  Five  days  later  he  came  down  with 
yellow  fever,  which  caused  his  death.  His  life  was  a  sacrifice  for  the 
benefit  of  the  human  race. 

Yellow  Fever  Mosquito.— The  mosquito  that  transmits  this  fever 
is  Aedes  argenteus  {Aedes  calopus,  Stegomyia  fasciata)  and  no  other 
species  is  as  yet  known  to  be  concerned  in  the  disease.  A.  argenteus  is 
limited  to  warm  regions;  at  a  temperature  less  than  68°  F.  the  eggs  do  not 
hatch,  and  below  62°  F.  the  female  does  not  bite  (Reed).  The  depend- 
ence of  the  insect  upon  warmth  for  its  development  explains  the 
cessation  of  the  disease  in  New  Orleans  in  December,  with  a  mean 
temperature  of  55.3°  F.  and  in  cities  farther  north  when  frost  comes. 
In  Cuba  and  Brazil  the  fever  has  occurred  every  month  in  the  year. 
Cause  of  Yellow  Fever. — The  specific  cause  of  yellow  fever  eluded 
detection  for  many  years  and  was  regarded  by  many  investigators  as 
being  ultra-microscopic.  The  U.  S.  Commission  produced  the  disease 
by  the  injection  of  blood  serum  that  had  been  passed  through  a  bacteria- 
proof  filter.  Blood  from  a  subject  in  whom  the  disease  had  been  pro- 
duced by  transfusion  was  capable  of  infecting  a  third  person. 

The  weight  of  evidence  indicated  that  the  unknown  cause  of  yellow 
fever  was  an  organism  rather  than  a  toxin,  and  in  19 19  the  organism  was 
discovered  by  Noguchi  to  be  a  spirochaete,  which  he  named  Leptospira 
icteroides.  During  his  investigations  in  Guayaquil  Noguchi  succeeded 
in  isolating  this  spirochaete  from  the  blood  of  patients  and  from  mos- 
quitoes as  well.  He  obtained  pure  cultures  of  the  parasite  by  inoculat- 
ing guinea  pigs  with  blood  from  patients,  and  was  able  to  produce  the 
disease  by  inoculation  in  guinea  pigs,  dogs  and  marmosets. 


256  ENTOMOLOGY 

Following  his  discovery,  Dr.  Noguchi,  of  the  Rockefeller  Institute 
for  Medical  Research,  prepared  from  the  organisms  a  vaccine,  which 
has  been  administered  to  many  thousand  persons  with  results  that  are 
reported  to  be  distinctly  encouraging. 

Control  of  Yellow  Fever. — The  preventive  measures  based  upon  the 
facts  learned  by  the  U.  S.  Army  Commission  were  wonderfully  suc- 
cessful. In  February,  1901,  Major  W.  C.  Gorgas  began  a  campaign  to 
eradicate  the  disease  in  Havana.  His  efforts  were  directed  against 
mosquitoes.  Every  case  of  fever  had  to  be  reported  promptly  to  the 
authorities.  Then  the  patient  was  isolated  and  all  the  rooms  in  the 
building  and  in  neighboring  houses  fumigated  and  the  doors  and 
windows  screened.  Standing  water  in  which  mosquitoes  might  develop 
was  drained  or  treated  with  petroleum,  and  water  tanks  and  barrels 
were  screened. 

In  September,  1901,  the  last  case  of  yellow  fever  arose  in  Havana, 
where  the  disease  had  prevailed  for  1 50  years,  with  an  annual  mortality 
of  500  to  1600  or  more.  Cases  are  now  and  then  brought  into  Havana 
from  Mexico  or  Central  America  but  are  treated  under  screens  in  the 
regular  hospitals  with  impunity. 

Yellow  Fever  in  New  Orleans. — In  1905  the  last  epidemic  of  yellow 
fever  occurred  in  New  Orleans.  It  might  have  been  checked  at  its 
inception  had  not  the  authorities  adopted  a  policy  of  secrecy  in  regard 
to  the  presence  of  the  disease.  The  city  was  freed  from  the  fever  before 
frost  came,  by  the  same  methods  that  had  proved  successful  in  Cuba; 
but  not  without  organized  work  of  the  most  strenuous  kind  on  the  part 
of  the  citizens,  under  the  direction  of  the  U.  S.  Public  Health  and 
Marine-Hospital  Service.  At  present  the  yellow  fever  mosquito  is 
said  to  be  a  rarity  in  Louisiana  owing  to  the  vigorous  measures  enforced 
in  its  suppression  throughout  the  state. 

Fever  in  the  Canal  Zone. — The  Panama  Canal  zone  was  formerly 
one  of  the  most  unhealthful  places  on  earth,  chiefly  on  account  of  the 
prevalence  of  malaria  and  yellow  fever.  When  the  United  States  ac- 
quired the  zone  in  1904  it  was  realized  that  the  first  step  toward  building 
the  great  canal  was  to  protect  the  health  of  all  those  immediately  con- 
cerned in  the  undertaking,  and  the  sanitation  of  the  isthmus  was  placed 
in  charge  of  one  eminently  quaHfied  for  the  work.  Colonel  W.  C.  Gorgas. 

He  adapted  the  methods  he  had  used  in  Cuba  to  the  conditions 
existing  on  the  isthmus,  with  the  result  that  every  year  the  death  rate 
decreased  until  in  1908  it  became,  among  eight  thousand  white 
Americans  living  there,  9.72  per  thousand,  "a  rate  no  higher  than  for  a 


TRAXs;\rissi(>x  of  diseases  by  insects  257 

similar  population  in  the  healthiest  localities  in  the  United  States,  and 
much  lower  than  that  for  most  parts  of  the  country."  The  Sanitary 
Department  has  succeeded  in  driving  yellow  fever  from  the  isthmus  and 
in  checking  malaria  and  other  diseases  to  such  a  degree  that  the  canal 
zone  is  no  longer  an  unhealthful  place. 

After  serving  as  Surgeon  General  of  the  United  States  Army  from 
1 9 14  to  19 1 8,  W.  C.  Gorgas  entered  the  service  of  the  International 
Health  Board,  and  was  organizing  an  international  campaign  against 
yellow  fever  at  the  time  of  his  death  in  London,  July  4,  1920. 

General  Gorgas  attained  international  preeminence  for  his  ability 
in  organizing  and  conducting  operations  of  magnitude  against  insect- 
borne  diseases.     On  account  of  his  services  in  the  protection  of  human 
life  his  assistance  was  sought  by  foreign  nations,  and  he  received  higHl  ^ 
honors.  .  •  /\ 

Typhoid  Fever  rv  r** 

Ski 

The  specific  cause  of  typhoid  fever  is  Bacillus  typhosus.     In  bBte^"" 
human  body  this  bacillus  occurs  chiefly  in  the  intestines;  but  also  in  ofieQ  * 
urinary  bladder  and  usually  in  the  blood  of  infected  persons. 

The  excreta  of  typhoid  subjects  contain  the  virulent  bacilli;  an(^s,| 
some  persons,  even  after  recovery,  continue  to  be  "chronic  carriers"  of 
the  disease  for  many  years. 

Transmission. — The  typhoid  bacillus  is  introduced  into  the  human 
system  by  eating  or  drinking.  Most  epidemics  are  due  to  infected 
water  and  many  to  milk;  occasionally  the  disease  is  acquired  from  raw 
vegetables  or  from  oysters  contaminated  with  sewage.  Often  the 
bacillus  is  conveyed  to  food  by  human  hands  and  possibly  it  is  some- 
times carried  by  dust,  cockroaches  or  ants;  but  there  is  no  doubt  that 
the  disease  is  transmitted  by  certain  flies,  particularly  the  true  house 
fly,  Muse  a  domes  tica,  which  is  by  far  the  commonest  fly  found  generally 
in  houses,  and  becomes  a  serious  menace  to  health  during  epidemics  of 
typhoid  fever. 

The  house  fly  is  well  adapted  by  its  structure  and  habits  to  carry 
bacteria.  The  adults  often  feed  on  substances  contaminated  with 
typhoid  or  other  bacteria  and  these  infected  substances  cling  readily 
to  the  hairs  of  the  insect,  especially  those  of  the  feet,  and  to  the  pro- 
boscis. The  larvse  develop  chiefly  in  horse  manure,  but  also  in  other 
kinds  of  excreta,  some  of  which  may  contain  virulent  typhoid 
bacilli. 


250  ENTOMOLOGY 

Transmission  by  Flies. — During  the  Spanish- American  war  typhoid 
fever  occurred  in  every  American  regiment  and  raged  in  many  of 
the  concentration  camps,  in  consequence  of  which  a  special  commission 
was  appointed  to  investigate  the  origin  and  spread  of  the  disease  in  the 
army.  A  report  by  one  of  the  members  of  the  commission,  Doctor 
Vaughan,  presents  the  following  conclusions: 

"a.  Flies  swarmed  over  infected  fecal  matter  in  the  pits  and  then 
visited  and  fed  upon  the  food  prepared  for  the  soldiers  at  the  mess  tents. 
In  some  instances  where  lime  had  recently  been  sprinkled  over  the  con- 
tents of  the  pits,  flies  with  their  feet  whitened  with  lime  were  seen 
walking  over  the  food. 

"6.  Officers  whose  mess  tents  were  protected  by  means  of  screens 
suffered  proportionally  less  from  typhoid  than  did  those  whose  tents 
were  not  so  protected. 

"c.  Typhoid  fever  gradually  disappeared  in  the  fall  of  1898,  with 
the  approach  of  cold  weather,  and  the  consequent  disabling  of  the  fly. 

"It  is  possible  for  the  fly  to  carry  the  typhoid  bacillus  in  two  ways. 
In  the  first  place,  fecal  matter  containing  the  typhoid  germ  may  adhere 
to  the  fly  and  be  mechanically  transported.  In  the  second  place,  it  is 
possible  that  the  typhoid  bacillus  may  be  carried  in  the  digestive  organs 
of  the  fly  and  may  be  deposited  with  its  excrement." 

Similar  conclusions  in  regard  to  the  agency  of  flies  in  the  spread  of 
enteric  fever  among  troops  have  been  reached  also  by  investigators  in 
Bermuda,  South  Africa  and  India. 

Firth  and  Horrocks  fed  house  flies  on  material  contaminated  with 
Bacillus  typhosus  and  then  obtained  cultures  of  the  bacillus  from  objects 
to  which  the  flies  had  access.  In  another  experiment  they  obtained 
cultures  from  the  heads,  bodies,  wings  and  legs  of  such  flies.  Other 
investigators  have  obtained  Bacillus  typhosus  from  flies  captured  in 
rooms  occupied  by  typhoid  cases. 

Faichnie  caught  flies  in  a  place  where  there  was  an  outbreak  of  ty- 
phoid fever,  held  them  on  a  sterilized  needle  and  passed  them  through  a 
flame  until  legs  and  wings  were  scorched;  after  which  he  obtained  the 
typhoid  bacillus  from  the  mashed  bodies  of  the  flies,  the  bacilli  having 
been  present  in  the  ahmentary  tract,  without  doubt. 

Faichnie  also  obtained  cultures  of  Bacillus  typhosus  from  the  intes- 
tines of  flies  which  had  developed  from  larvae  fed  on  feces  containing  the 
bacillus. 

Jordan  states  that  the  bacilli  survive  the  passage  of  the  ahmentary 
canal  of  the  fly. 


TRANSMISSION    OF    DISEASES    BY    INSECTS  259 

Ficker  recovered  typhoid  bacilli  from  flies  twenty-three  days  after 
they  had  been  infected. 

In  fact,  a  great  amount  of  evidence  has  accumulated  proving  that 
flies  transmit  not  only  the  bacilli  of  typhoid  fever,  but  many  other 
bacteria,  and  often  in  enormous  numbers.  For  example,  Esten  and 
Mason  in  their  study  of  the  sources  of  bacteria  in  milk,  collected  and 
examined  flics  from  stables,  pig-pens,  houses  and  other  places,  and  found 
an  average  of  1,222,570  bacteria  per  fly;  the  majority  of  these  being 
objectionable  kinds  of  bacteria. 

Musca  Domestica. — A  single  female  of  the  common  house  fly  lays 
in  all  some  six  hundred  eggs.  In  midsummer,  in  Washington,  D.  C, 
the  eggs  hatch  in  about  eight  hours;  the  larval  period  is  from  four  to 
five  days  and  the  pupal  period  five  days,  making  the  cycle  about  ten 
days  in  length.  In  cooler  parts  of  the  season  the  cycle  requires  more 
time  and  in  warm  climates  it  may  be  as  short  as  eight  days.  The 
number  of  generations  in  Washington  is  probably  not  more  than 
nine  (Howard). 

Control. — One  of  the  best  baits  for  flies  in  houses  is  formalin,  which 
is  poisonous  to  flies  but  harmless  to  man.  This  is  prepared  by  diluting 
formaldehyde  with  five  or  six  times  as  much  water  and  exposing  it  in 
shallow  dishes,  the  addition  of  a  little  sugar  or  milk  making  the  solution 
more  attractive  to  flies,  which  drink  it  and  quickly  die.  Pyrethrum  is 
efl'ective  against  flies,  but  only  when  it  is  pure  and  has  been  kept  from 
exposure  to  the  air.  Pyrethrum,  the  chief  basis  of  all  the  common 
insect  powders,  is  applied  by  being  puffed  through  a  bellows  or  by  being 
burned.  The  powder  may  be  moistened  and  shaped  into  cones  which 
when  lighted  at  the  top  burn  slowly  and  give  off  fumes  that  are  suffocat- 
ing to  insects. 

Dr.  Howard  estimates  that  more  than  ten  million  dollars  are  spent 
every  year  in  screening  houses  in  the  United  States.  Another  enormous 
sum  is  spent  for  fly  papers  and  fly  traps.  The  efficient  way  to  deal  with 
the  fly  problem,  however,  is  to  prevent  the  insects  from  breeding,  Ex- 
crementitious  substances  should  be  enclosed  in  such  a  way  as  to  prevent 
the  access  of  flies,  or  should  be  treated  in  a  way  to  kill  the  larvae  therein; 
one  of  the  simplest  methods  of  treating  stable  manure  being  to  spread 
it  out  to  dry,  since  the  maggots  cannot  develop  without  moisture. 

For  detailed  information  on  everything  of  importance  relating  to 
the  house  fly,  and  particularly  on  the  mitigation  of  the  fly-nuisance  by 
concerted  action  in  communities,  Dr.  Howard's  admirable  book  on  the 
house  fly  should  be  consulted. 


26o  ENTOMOLOGY 

Plague 

In  the  ancient  history  of  Europe  epidemics  of  plague  occupy  a  large 
place.  For  many  years  this  pestilence  has  thrived  in  China  and  India, 
and  following  an  outbreak  in  1894  in  Hong  Kong,  the  plague  reached 
the  western  hemisphere  for  the  first  time,  appearing  in  Brazil,  Argentina 
and  other  South  American  countries,  in  Mexico  and  San  Francisco. 

The  cause  of  plague  is  Bacillus  pestis,  an  organism  abundant  in  the 
secretions  and  excretions  of  plague-stricken  animals. 

Three  varieties  of  the  disease  are  distinguished  as  follows: 

(i)  the  bubonic,  in  which  the  bacilli  cause  enlargements  of  lymphatic 
glands ; 

(2)  the  septiccBmic,  characterized  by  the  presence  of  large  numbers 
of  bacilli  in  the  blood  and  highly  virulent; 

(3)  the  pneumonic,  in  which  the  respiratory  organs  are  affected,  the 
sputum  showing  the  bacilli  in  enormous  numbers;  this  form,  relatively 
rare,  is  the  most  fatal. 

Transmission. — Plague  is  primarily  a  disease  of  rats,  an  epidemic 
of  plague  in  these  animals  having  often  been  observed  to  precede  as 
well  as  accompany  an  epidemic  among  human  beings.  The  disease 
affects  also  mice,  cats,  dogs,  calves,  sheep,  pigs,  ducks,  geese  and  many 
other  animals. 

Though  rats  and  other  of  the  lower  animals  may  contract  the  septi- 
caemic  type  of  the  disease  from  feeding  on  parts  of  animals  killed  by 
plague  or  on  cultures  of  Bacillus  pestis,  the  disease  is  commonly  trans- 
mitted among  rats  neither  by  contact  nor  through  the  atmosphere,  but 
by  means  of  fleas.  Healthy  rats  in  association,  with  diseased  rats  do 
not  become  infected  as  long  as  fleas  are  excluded;  but  a  transfer  of  fleas 
from  the  latter  to  the  former  starts  the  disease.  By  various  experi- 
ments the  Indian  Plague  Commission  demonstrated  the  important  part 
played  by  rat-fleas  in  the  transmission  of  plague.  Zirolia  found  that 
the  bacilli  even  multiply  in  the  mid-intestine  of  the  flea,  retaining  their 
virulence  for  a  week  or  more.  Bacot  found  that  the  European  rat-flea 
{Ceraiophyllus  fasciatus)  remained  infective,  when  isolated  from  a 
host,  for  forty-seven  days. 

The  weight  of  evidence,  both  observational  and  experimental, 
shows  that  plague  is  transmitted  from  rats  to  man  by  several  species 
of  fleas  and  also  by  bedbugs.  Verjbitski,  whose  experiments  on  this 
subject  were  particularly  precise  and  thorough,  found  that  plague  can 
be  conveyed  by  the  bites  of  these  insects  and  that  the  opening  made 


TRANSMISSION    OF    DISEASES   BY    INSECTS  261 

by  the  bite  affords  entrance  to  plague  bacilli  when  the  bodies  of  the 
insects  are  crushed  or  when  the  infected  feces  are  introduced  by  the 
rubbing  or  scratching  of  the  wound. 

The  species  of  rat-flea  most  common  in  the  orient  is  the  cosmo- 
politan "plague  flea,"  Xenopsylla  cheopis. 

In  the  United  States  the  most  common  rat  flea  is  Ceratophyllus 
j'asciatus.  The  common  cat  and  dog  flea,  Clenocephalus  canis,  affects 
rats  as  does  the  human  flea,  Pulex  irritans;  and  all  these  species  are 
known  to  bite  man. 

Plague  in  San  Francisco. — Plague,  long  dreaded  in  American  sea- 
ports, Anally  entered  San  Francisco  in  1900,  killed  114  persons  in  the 
next  four  years,  became  dormant  and  broke  forth  again,  with  violence, 
in  1907.  The  city,  just  beginning  to  recover  from  the  great  fire  of  the 
year  before,  was  in  a  frightful  sanitary  condition  and  most  of  the  popu- 
lation, engaged  in  the  work  of  reconstruction,  paid  little  attention  to 
the  deaths  from  plague  and  at  first  gave  little  aid  toward  the  suppression 
of  the  disease.  As  may  be  imagined,  the  campaign  against  the  dis- 
ease undertaken  by  the  U.  S.  Public  Health  and  Marine-Hospital 
Service  was  carried  on  in  the  face  of  great  odds.  It  was,  however,  con- 
ducted most  efficiently  and  successfully  under  the  command  of  Dr. 
Rupert  Blue  (later  Surgeon-General),  who  wisely  attacked  the  disease 
by  attacking  the  rat  population. 

The  labor  involved  in  starving  out  the  rats,  trapping  or  poisoning 
them,  and  making  buildings  rat-proof  by  the  use  of  concrete  or  sheet 
iron,  was  immense;  but  the  undertaking  was  nevertheless  carried  to  a 
successful  conclusion.  More  than  one  million  rats  were  killed  and  the 
disease  was  checked. 

In  California  plague  affects  ground  squirrels,  which  doubtless  con- 
tract the  disease  from  the  rats  that  use  the  runways  of  the  squirrels  in 
the  fields. 

Trypanosomiases 

Some  of  the  diseases  known  as  trypanosomiases  are  among  the  dead- 
liest that  affect  man  and  other  vertebrates,  and  pathogenic  trypano- 
somes — the  organisms  causing  these  diseases — have  received  an 
immense  amount  of  study  during  recent  years. 

Trypanosomes. — The  organisms  under  consideration  are  flagellate 
protozoans.  A  typical  trypanosome,  for  example,  T.  lewisi  (Fig.  274) 
of  the  rat,  is  essentially  an  elongated  cell,  tapering  at  each  end,  serpen- 


262 


ENTOMOLOGY 


tine  in  form  and  with  no  definite  cell-wall.  A  round  or  oval  nucleus  is 
present,  also  a  peculiar  chromatin  body  situated  often  near  the  poste- 
rior end  of  the  cell  and  termed  the  hlepharoplast.  Along  one  side  of  the 
cell  is  a  delicate  protoplasmic  contractile  membrane,  the  undulating 
membrane,  along  the  edge  of  which  is  a  marginal  cord,  which  arises  by- 
growth  from  the  hlepharoplast  and  is  continued  beyond  the  anterior 
end  of  the  cell  as  a  vibratile  flagellum. 

Asexual  reproduction  is  by  means  of  a  longitudinal  division  of  the 
cell  body,  preceded  by  division  of  the  flagellum,  hlepharoplast  and 
nucleus,  the  nucleus  dividing  amitotically.  In 
regard  to  the  existence  of  sexual  stages,  or 
gametes,  the  results  of  investigators  seem  to 
be  inconclusive  as  yet. 

In  a  film  of  fresh  blood  under  the  microscope, 
any  active  trypanosomes  in  the  field  of  view 
attract  attention  as  centers  of  commotion  among 
the  red  blood  corpuscles,  which  are  pushed  aside 
by  the  lashing,  twisting  and  other  movements  of 
the  trypanosomes. 

The  nutrition  is  by  means  of  osmosis.  Try- 
panosomes have  not  been  seen  to  attack  erythro- 
cytes, but  according  to  MacNeal  and  Novy 
haemoglobin  is  useful  if  not  indispensable  to 
them. 

All  five  classes  of  vertebrates  serve  as  hosts 
for  trypanosomes,  of  which  more  than  seventy 
species  have  received  names.  Most  of  these 
species  are  carried  from  one  vertebrate  host  to 
another  by  means  as  yet  unknown,  but  about 
20  per  cent,  are  known  or  suspected  to  be 
transmitted  by  an  intermediate  invertebrate  host.  Thus  trypano- 
somes of  frogs  are  conveyed  by  leeches ;  pigeons  are  infected  by  mos- 
quitoes, rats  by  sucking  lice  and  fleas,  and  many  mammals  through  the 
agency  of  blood-sucking  flies  of  the  genus  Glossina,  and  probably  also 
by  Stomoxys  and  certain  Tabanidee. 

Tsetse  Flies. — The  name  tsetse  fly,  originally  limited  to  Glossina 
morsitans  (Muscidse)  is  now  used  for  any  of  the  fifteen  known  species 
of  the  genus.  These  flies  are  a  little  larger  than  the  common  house  fly 
{Musca  domestica) .  Their  wings,  in  the  resting  position,  overlap  exactly 
(Fig.  275)  instead  of  being  separated  at  the  tips.     The  proboscis  pro- 


2  74. — Trypano- 
soma lewisi.  b,  hlepharo- 
plast; /,  flagellum;  m, 
marginal  cord;  w.  nucleus; 
tt,  undulating  membrane. 
Greatly  magnified. 


TRANSMISSION   OF   DISEASES   BY   INSECTS 


263 


Fig. 


275. — Tsetse  fly,   Glossina 
morsilans.     X  2}^^. 


jects  forward,  and  is  stout,  owing  to  the  ensheathing  palpi;  the  base  of 
the  labium  forms  a  prominent  bulb.  These  are  the  more  conspicuous 
characters  that  serve  to  distinguish  tsetse  flies  from  other  blood-sucking 
flies  with  which  they  might  be  confused. 

The  mode  of  reproduction  as  described  by  Brauer  is  similar  to  that 
of  the  group  of  parasitic  flies  known  as  Pupipara.     The  fly  produces  a 
full-grown  larva,  which  at  once  creeps  to 
some    resting    place    and    forms    a    black 
puparium. 

Tsetse  flies  frequent  hot,  humid  regions, 
near  bodies  of  water,  and  are  restricted  to 
shaded  situations,  never  occurring  on  the 
open  plains.  Both  sexes  are  bloodthirsty 
but  bite  only  during  the  daytime  as  a  rule; 
though  they  may  bite  at  night  when  the 
moonlight  is  bright.  Travelers  take  advan- 
tage of  the  habits  of  the  fly  to  journey  by 
night;  spending  the  day  in  an  open  unin- 
fested  place. 

Nagana. — The  colon'zation  of  South 
Africa  was  greatly  retarded  by  nagana,  a  disease  invariably  fatal  to 
the  horse,  donkey  and  dog,  and  usually  fatal  to  cattle,  but  not  affect- 
ing man.  Livingstone  and  other  explorers  in  regions  where  nagana  is 
prevalent  record  their  having  been  bitten  by  tsetse  flies  thousands  of 
times  with  no  result  other  than  a  slight  irritation. 

Bruce  was  the  first  to  prove  the  identity  of  nagana  and  tsetse-fly 
disease  and  to  demonstrate  the  role  of  the  fly  in  the  transmission  of  the 
disease.  His  investigations,  begun  in  Zululand  in  1894,  are  of  funda- 
mental importance  and  have  given  an  immense  stimulus  to  the  study 
of  trypanosomes. 

After  finding  that  no  bacteria  were  concerned  in  nagana,  Bruce  dis- 
covered trypanosomes  in  the  blood  of  cattle  affected  with  the  disease. 
He  inoculated  their  blood  into  healthy  horses  and  dogs  and  in  a  few  days 
the  blood  of  these  animals  was  teeming  with  trypanosomes.  Then  he 
took  healthy  animals  from  the  mountain  on  which  he  had  located  his 
headquarters  down  into  the  "fly  country;"  there  they  contracted  the 
tsetse-fly  disease  and  showed  in  their  blood  trypanosomes  indistinguish- 
able from  those  of  nagana. 

Horses  taken  into  the  fly  country  but  not  allowed  to  eat  or  drink 
there,  took  the  disease;  furthermore,  supplies  of  grass  and  water  brought 


264 


ENTOMOLOGY 


from  the  fly  country  and  fed  to  healthy  horses  failed  to  convey  the 
disease. 

Then  the  influence  of  the  fly  was  tested.  Tsetse  flies  caught  in  the 
lowland,  carried  to  the  mountain  and  placed  at  once  on  healthy  animals 
gave  rise  to  the  disease;  but  the  flies  never  retained  the  power  of  infect- 
ing a  healthy  animal  for  more  than  forty-eight  hours  after  feeding  upon 
a  sick  animal.  Thus  wild  flies,  kept  without  food  for  three  days  and 
then  fed  on  a  healthy  dog,  never  gave  rise  to  the  disease.  The  fly  alone 
transmitted  the  disease;  and  this  by  means  of  trypanosomes  adhering 
to  the  proboscis  either  inside  or  out.  Bruce  found 
these  organisms  in  the  digestive  tract  also,  but 
with  no  change  in  their  form. 

He  discovered  further  that  buffaloes,  antelopes 
and  many  other  wild  animals  carried  the  parasite 
in  their  blood,  and  was  able  by  injecting  this 
blood  to  transmit  the  disease  to  healthy  domesti- 
cated animals.  The  parasites  were  never  numer- 
ous in  the  blood  of  their  wild  hosts,  however,  and 
the  latter  seemed  to  be  unaffected  by  their  pres- 
ence. The  ''big  game"  of  Africa  serves,  gener- 
ally speaking,  as  a  reservoir  for  supplies  of 
trypanosomes. 

The  species  of  parasite  that  Bruce  studied  is 
named  Trypanosoma  hrucei  (Fig.  276).     The  flies 
concerned  are  Glossina  morsitans,  G.  pallidipes  and 
G.fusca,  particularly  the  first  two,  the  distribution 
of  which  coincides  with  that  of  nagana. 

No  certain  remedies  for  the  disease  are  yet  known.  Human  serum 
injected  into  infected  animals  causes  the  trypanosomes  to  disappear, 
at  least,  temporarily;  but  this  fact  is  of  more  scientific  interest  than 
practical  importance.  The  precaution  of  traveling  by  night  is  often 
adopted.  Creolin  and  some  other  substances  rubbed  on  animals 
serve  to  repel  the  flies,  and  the  smoke  of  encampments  drives  them  away. 
The  protection  of  horses  by  means  of  screens  is  of  course  effective. 

Human  Trypanosomiasis. — Sleeping  sickness  is  most  prevalent  in 
the  Congo  basin,  whence  it  has  spread  rapidly  in  equatorial  Africa,  where 
it  kills  about  fifty  thousand  natives  every  year.  The  reported  cases  of 
recovery  are  so  extremely  rare  that  the  mortality  is  placed  at  one 
hundred  per  cent. 

In  the  first  stage  of  the  disease,  marked  by  the  appearance  of 


-Trypano- 


FiG.    276 
S07na     brucei.     Greatly 
magnified. 


TRANSMISSION   OF   DISEASES   BY   INSECTS  265 

trypanosomes  in  the  blood,  negroes  show  no  symptoms  as  a  rule,  though 
whites  are  subject  to  fever.  The  symptoms  may  appear  as  early  as 
four  weeks  after  infection  or  as  late  as  seven  years. 

In  the  second  stage  trypanosomes  appear  in  the  cerebro-spinal  fluid 
and  in  large  numbers  in  the  lymphatic  glands,  those  of  the  neck,  axillae 
and  groins  becoming  enlarged.  There  is  tremor  of  the  tongue  and 
hands,  drowsiness,  emaciation  and  mental  degeneration.  The  drowsi- 
ness passes  into  periods  of  lethargy  which  become  gradually  stronger 
until  the  patient  becomes  comatose  and  dies.  Some  victims  do  not 
sleep  excessively,  but  are  lethargic,  and  "profoundly  indifferent  to  all 
going  on  around  them." 

There  is  some  disagreement  among  authors  as  to  the  precise  effects 
of  trypanosomes  on  human  tissues  and  organs,  but  the  evidence  indi- 
cates at  least  that  trypanosomes  produce  a  toxin  which  sets  up  irrita- 
tions of  the  lymphatic  glands  in  general  and  those  of  the  brain  in 
particular.  Many  of  the  symptoms  of  trypanosomiasis  are  traceable 
primarily  to  inflammation  of  the  lymphatics  of  the  nervous  system. 

The  specific  cause  of  sleeping  sickness  is  T.  gambiense,  discovered  in 
1 901  by  Forde  and  named  by  Button.  Two  eminent  English  investi- 
gators of  sleeping  sickness,  Button  and  TuUock,  sacrificed  their  lives  to 
the.  disease  they  were  studying. 

As  the  result  of  the  labors  of  many  investigators,  human  trypano- 
somiasis is  now  well  understood.  Bruce  and  Nabarro  demonstrated  by 
means  of  inoculation  experiments  with  monkeys  that  T.  gambiense  is 
transmitted  chiefly,  if  not  solely,  by  a  tsetse  fly,  Glossina  palpalis. 
They  and  Greig  showed  that  the  distribution  of  the  disease  in  Uganda 
coincided  with  that  of  the  fly.  In  some  regions  where  the  fly  is  present 
the  disease  is  unknown;  which  means  simply  that  cases  of  the  disease 
have  not  yet  been  introduced. 

Notwithstanding  the  great  activity  in  the  study  of  this  disease  no 
good  remedy  for  it  has  been  found.  Wise  travelers  in  tropical  Africa 
take  every  precaution  against  being  bitten  by  tsetse  flies.  Much  effort 
is  being  exerted  to  check  the  spread  of  the  disease  among  the  natives  in 
some  of  the  infected  regions;  chiefly  by  removing  patients  from  the  fly 
region,  by  screening  dwellings  or  by  building  them  away  from  the  dainp 
and  marshy  areas  where  the  flies  breed. 

FiLARIASIS 

The  first  disease  found  to  be  transmitted  by  an  insect  was  filariasis, 
the  subject  of  important  investigations  by  Manson,  Bancroft  and  others. 


266  ENTOMOLOGY 

This  disease  of  tropical  and  subtropical  regions  is  caused  by  a  thread- 
worm, or  nematode,  known  as  Filaria  bancrofti,  which  occurs  in  the 
blood  of  man  and  of  several  of  the  lower  animals  as  a  slender  larva 
(microfilaria)  about  one-quarter  of  a  millimeter  in  length.  At  night 
these  larvse  swarm  in  the  peripheral  circulation,  from  which  they  are 
taken  into  the  ahmentary  canal  of  a  blood-sucking  mosquito  (chiefly 
Culex  quinquefasciatus) .  In  the  mid-intestine  of  the  mosquito  the  larva 
escapes  from  its  sheath  and  penetrates  into  muscular  tissue,  where  it 
grows  and  develops  for  two  or  three  weeks,  after  which  it  goes  to  some 
other  part  of  the  mosquito's  body,  often  to  the  base  of  the  proboscis, 
whence  the  larvae  are  carried  into  the  blood  of  some  vertebrate  host, 
there  to  develop  to  sexual  maturity. 

The  larvae  are  often  common  in  human  blood  without  seeming  to 
injure  the  host  in  any  way,  but  the  adults  (three  or  four  inches  long  and 
often  found  in  groups)  and  ova  that  have  escaped  from  the  parent 
female  sometimes  obstruct  the  lymphatic  canals  and  cause  enormous" 
swellings  of  feet,  legs,  arms  or  other  parts  of  the  human  body;  this 
condition  being  known  as  elephantiasis. 

Typhus 

War  and  typhus  have  always  gone  hand  in  hand.  Crowded  and 
uncleanly  conditions  in  camps  and  prisons  are  most  favorable  to  the 
propagation  of  the  disease. 

Recent  History. — The  last  scourge  of  typhus  in  Serbia  began  in 
October,  19 14  among  Austrian  prisoners,  who  spread  the  disease  over 
the  country.  No  adequate  means  of  checking  the  disease  existed,  and 
in  January,  191 5  the  epidemic  was  raging.  In  April  there  were  9,000 
deaths  per  day;  the  total  mortahty  for  the  first  five  months  of  191 5 
being  more  than  100,000.  This  epidemic  was  checked  largely  by  the 
energetic  efforts  of  Dr.  R.  P.  Strong  and  his  fellow- workers. 

Syria  suffered  from  typhus  in  191 6,  with  more  than  1,000  deaths 
daily.  In  Roumania,  1916-1919,  the  mortahty  was  26,000.  Mexico 
City  had  11,000  cases  of  typhus  in  December,  1915.  In  the  United 
States  the  disease  occurs  now  and  then  in  a  small  way,  but  especially 
among  immigrants. 

Cause. — The  specific  cause  of  typhus  can  not  as  yet  be  named  with 
certainty.  It  may  be  a  certain  spirochaete  discovered  in  191 7'  by 
Futaki,  who  found  it  in  the  liver  and  urine  of  typhus  victims,  as  well  as 
in  a  monkey  after  inoculation  with  infected  human  blood.  Others 
have  ascribed  the  disease  to  bacilli. 


TRANSMISSION    OF   DISEASES  BY   INSECTS  267 

Transmission. — Whatever  the  organism  may  be,  the  fact  is  now 
established  that  typhus  is  transmitted  by  human  lice.  Nicolle,  Comte 
and  Conseil,  working  in  northern  Africa  (1909),  conveyed  the  disease 
by  the  injection  of  human  blood  to  a  chimpanzee;  then  from  the 
chimpanzee  to  a  macaque  monkey;  and,  by  means  of  human  body  lice, 
from  this  animal  to  other  monkeys.  Drs.  Ricketts  and  Wilder 
performed  similar  experiments  in  Mexico  City  (19 10)  with  similar 
results.  They  found  that  monkeys  kept  free  from  lice  remained 
healthy,  but  contracted  the  disease  after  inoculation  by  means  of  body 
lice  which  had  fed  on  the  blood  of  typhus  patients.  They  showed  also 
the  strong  probability  that  infection  is  transmitted  through  the  eggs 
to  the  next  generation  of  lice,  which  through  this  indirect  infection  can 
cause  typhus  in  monkeys  and  presumably  in  man  also.  It  has  been 
found  that  both  the  body  louse  {Pediculus  corporis)  and  the  head  louse 
{P.  capitis)  transmit  typhus,  but  bedbugs  and  fleas  are  not  impHcated. 

The  brilliant  work  of  Dr.  H.  T.  Ricketts  was  cut  short  by  his  death, 
in  191  o,  from  typhus  contracted  during  his  experiments. 

Control. — A  typhus  patient  is  harmless  as  a  source  of  contagion  in 
the  absence  of  human  Hce,  the  agents  of  transmission.  Lice,  as  is  well 
known,  crawl  readily  from  man  to  man  in  crowded  quarters,  and  inhabit 
the  clothing  as  well  as  the  body,  particularly  the  underclothing,  the 
seams  of  which  may  contain  the  eggs  in  immense  numbers.  Eradica- 
tion of  lousiness  means  freedom  from  typhus.  During  the  World  War, 
Great  Britain,  France  and  Germany  were  successful  in  protecting  their 
armies  from  the  ravages  of  typhus  by  the  use  of  methods,  often  elabo- 
rate, directed  against  the  Hce,  or  "cooties."  These  methods,  which 
are  generally  known,  consisted  of  (i)  the  thorough  cleansing  of  the 
surface  of  the  human  body;  (2)  the  disinfection  of  clothing  and  other 
belongings,  and  of  the  living  quarters,  by  various  physical  or  chemical 
processes. 

Relapsing  Fever 


Relapsing  or  recurrent  fever  is  less  fatal  than  typhus,  but  Hke  the 
latter  is  conveyed  by  lice  (though  not  exclusively)  and  accompanies 
war.  The  disease  has  often  raged  in  Europe;  the  last  epidemic,  early 
in  the  recent  war,  being  exceptionally  severe  in  Serbia. 

The  cause  of  relapsing  fever  is  the  genus  Spirochceta,  of  which 
different  species  produce  various  types  of  the  disease  in  different  parts 
of  the  world. 


268  -  ENTOMOLOGY 

Nicolle  and  his  colleagues  demonstrated  in  1913  that  the  European 
and  North  African  form  of  the  disease  is  transmitted  by  the  body 
louse,  and  the  head  louse  as  well,  though  not  by  their  bites.  When 
the  lice  are  crushed  and  the  infected  contents  of  their  bodies  rubbed  into 
wounds  made  by  the  lice,  or  into  abrasions  of  the  skin,  or  are  transferred 
as  by  the  fingers  to  a  mucous  membrane,  such  as  the  conjunctiva  of 
the  eye,  the  disease  is  produced. 

It  was  proved  that,  in  some  instances  at  least,  infection  could  be 
transmitted  through  the  eggs  to  the  lice  of  the  next  generation.  The 
European  form  of  the  disease  may  be  conveyed  by  the  bedbug  also, 
according  to  some  investigators.  In  central  Africa  a  common  tick 
is  the  agent  of  transmission,  and  in  Mexico  and  Central  America  ticks 
and  bedbugs  are  suspected. 

Trench  Fever 

One  of  the  most  disabling  diseases  in  the  Great  War  was  trench 
fever.  The  experiments  made  by  British  and  American  investigators 
in  19 1 8  proved  that  this  disease  also  is  transmitted  by  the  body  louse, 
Pediculus  corporis.  The  physical  cause  of  the  fever  is  conveyed  in  the 
feces  of  the  lice  and  inoculation  occurs  through  scratching  by  the  victim, 
and  possibly  also  by  means  of  punctures  made  by  the  hce.  The  specific 
cause  of  trench  fever  is,  however,  not  actually  known  as  yet. 

Other  Diseases 

Cholera  is  undoubtedly  transmitted  by  flies.  As  long  ago  as  1899 
Dr.  Nuttall  wrote:  "The  body  of  evidence  as  to  the  role  of  flies  in  the 
diffusion  of  cholera  is,  I  believe,  absolutely  convincing." 

Dysentery  is  probably  carried  by  fhes,  as  Dr.  Orton  and  others  have 
inferred  from  their  experiments. 

Spillman  and  Haushalter,  as  well  as  several  others,  examined  flies 
that  had  fed  on  tubercular  sputum  and  found  in  the  intestinal  contents 
and  in  the  dejections  of  these  flies  the  bacilli  of  tuberculosis. 

Dr.  F.  T.  Lord  summarizes  his  important  investigations  on  this 
subject  as  foflows: 

"  I.  Flies  may  ingest  tubercular  sputum  and  excrete  tubercle  bacilli, 
the  virulence  of  which  may  last  for  at  least  fifteen  days. 

"2.  The  danger  of  human  infection  from  the  tubercular  fly-specks 
is  by  the  ingestion  of  the  specks  on  food.     Spontaneous  liberation  of 


TRANSMISSION    OF    DISEASES   BY    INSECTS  269 

tubercle  bacilli  from  fly-specks  is  unlikely.     If  mechanically  disturbed, 
infection  of  the  surrounding  air  may  occur." 

If  it  is  true  that  tuberculosis  can  be  transmitted  by  means  of  food, 
as  experiments  with  some  of  the  lower  animals  seem  to  indicate,  the 
house  fly  is  evidently  a  factor  that  must  be  reckoned  with  in  the  fight 
against  this  disease. 

There  is  conclusive  evidence  that  Egyptian  ophthalmia  is  trans- 
mitted by  flies  and  it  is  highly  probable  that  certain  other  infections 
of  the  eye  are  conveyed  by  the  same  means. 

The  bacillus  of  the  deadly  disease  anthrax  can  be  transmitted  by 
tabanid  flies  and  stable  flies,  Stomoxys. 

Dr.  H.  Graham  and  others  have  proved  that  dengue  is  conveyed  by 
two  species  of  mosquitoes,  the  common  house  mosquito  of  the  tropics 
{Culex  quinquejasciatus)  and  the  yellow  fever  mosquito  {Aedes  argenteus). 

Phlebotomus  fever  of  Mediterranean  regions  and  India  is  known  to 
be  carried  by  a  sand  iiy,  Phlebotomus;  and  the  peculiar  Oroya  fever  of 
Peru  is  possibly  transmitted  by  a  fly  of  the  same  genus. 

There  is  partial  proof  that  the  destructive  kala-azar  in  India  is 
disseminated  by  the  common  Indian  bedbug. 

Tropical  sore  is  probably  spread  by  flies  of  some  kind. 

In  Ceylon,  the  skin  disease  known  as  yaws  is  conveyed  by  the  com- 
mon house  fly,  Musca  domestica;  and  in  the  West  Indies,  probably  by 
common  flies  of  the  genera  Oscinis  and  Sarcophaga. 

In  191 2  Professor  M.  J.  Rosenau  and  Dr.  C.  T.  Brues  announced 
that  they  had  succeeded  in  transmitting  infantile  paralysis  (polio- 
myelitis) to  monkeys  by  means  of  the  stable  fly,  Stomoxys  calcitrans, 
and  their  results  were  confirmed  by  Dr.  J.  F,  Anderson.  Whether 
this  is  the  usual  means  of  transmission  among  human  beings  it  remains 
to  be  determined.  There  is  also  some  experimental  evidence  that  the 
disease  may  be  carried  by  the  bedbug. 

Rocky  Mountain  spotted  fever  was  proved  by  Ricketts  in  1906 
to  be  conveyed  by  two  or  more  common  species  of  wood  ticks  of  the 
genus  Dermacentor. 

Smith  and  Kilborne  demonstrated  that  the  destructive  Texas  fever 
of  cattle,  due  to  a  protozoan  parasite,  is  transmitted  by  a  common  tick 
Margaropus  annulatus.  The  adoption  of  methods  of  pasturing  that 
enable  cattle  to  avoid  the  ticks  has  been  highly  successful. 


CHAPTER  X 


INTERRELATIONS  OF  INSECTS 


Insects  in  general  are  adapted  to  utilize  all  kinds  of  organic  matter 
as  food,  and  they  show  all  gradations  of  habit  from  herbivorous  to  carniv- 
orous. The  many  forms  that  derive  their  food  from  the  bodies  of  other 
insects  may  conveniently  be  classed  as  predaceous  or  parasitic. 

Predaceous  Insects. — Among  Orthoptera,  Mantidae  are  notably 
predatory,  their  front  legs  (Fig.  64,  C)  being  well  fitted  for  grasping  and 
killing  other  insects.  The  predaceous  odonate  nymphs  have  a  peculiar 
hinged  extensible  labium  with  which  to  gather  in  the  prey.  The  adults 
catch  with  surpassing  speed  and  precision 
a  great  variety  of  flying  insects,  mostly 
small  forms,  but  occasionally  butterflies  of 
considerable  size.  The  eyes  of  a  dragon 
fly  are  remarkably  large;  the  legs  form  a 
spiny  basket,  probably  to  catch  the  prey, 
which  is  instantly  stripped  and  devoured, 
these  operations  being  facilitated  by  the 
»  excessive    mobility    of    the    head.     The 

f'  hemipterous  families  Corixidae,  Notonec- 

%  tidae    (Fig.    227),    Nepidae,    Belostomidae 

(Fig.  23),  Naucoridae  (Fig.  64,  D)  Redu- 
viidae  and  Phymatidae  are  predaceous,  with 
raptorial  front  legs  and  sharp  beaks. 
Some  of  the  Pentatomidae  (Fig.  277)  are 
of  considerable  economic  value  on  account 
of  their  predaceous  habits.  Most  of  the  Neuroptera  feed  upon  other 
insects.  The  Myrmeleon  larva  (ant-lion)  digs  a  funnel-shaped  pitfall, 
at  the  bottom  of  which  it  buries  itself  to  await  the  fall  of  some 
unlucky  ant.  The  Chrysopa  larva  (aphis-lion)  impales  an  aphid  on 
the  points  of  its  mandibles  and  sucks  the  blood  through  a  groove 
along  each  mandible  (Fig.  46,  E),  the  maxilla  fitting  against  this 
groove  to  form  a  closed  channel.  Several  families  of  Coleoptera 
are  almost  entirely  predaceous.  Among  aquatic  beetles,  Dytiscidae 
are  carnivorous  both  as  larvae  and  imagines,  Gyrinidag  subsist  chiefly 

270 


Fig.  277. — Nymph  of  Podisus 
maculivenlris  sucking  the  blood 
from  a  clover  caterpillar,  Colias 
philodice.     Natural  size. 


INTERRELATIONS    OF    INSECTS  27 1 

upon  disabled   insects,    but    occasionally   eat   plant   substances,    and 
Hydrophilidas  as  larvae  catch  and  devour  other  insects,  though  some 
of  the  beetles  of  this  family  {H.  triangularis,  for  example,  Fig.  229)  feed 
largely  if  not  entirely  upon  vegetation.     Of  terrestrial  Coleoptera,  the 
tiger  beetles  (Cicindelidae)  are  strictly  predaceous  upon  other  insects. 
The  Cicindela  larva  lives  in  a  burrow  in  the  soil  and  lies  in  wait  for 
passing  insects;  a  pair  of  hooks  on  the  fifth  segment  of  the  abdomen 
serves  to  prevent  the  larva  from  being  jerked  out  of  its  burrow  by  the 
struggles  of  its  captive.     The  large  family  Carabidae  is  chiefly  predace- 
ous; these  "running  beetles,"  both  as  larvae  and  adults  easily  overtake 
and  capture  other  terrestrial  insects.     The  Carabidae,  are  by  no  means 
exclusively  carnivorous,  however,  for  many  of  them  feed  to  some  extent 
upon  fungus  spores,  pollen,  ovules,  root-tips  and  other  vegetable  matter, 
as  Forbes  has  found ;  Harpalus  caliginosus  eats  the  pollen  of  the  ragweed 
in  autumn ;  Galerita  janus  eats  caterpillars  and  occasionally  the  seeds 
of  grasses;  but  Calosoma  appears  to  be  strictly  carnivorous,  feeding 
chiefly  upon  caterpillars  and  being  in  this  respect  of  considerable 
economic  importance.     As  a  whole,  Carabidae  prefer  animal  food,  as 
appears  from  the  fact  that  when  canker  worms,  for  instance,  are  unusu- 
ally abundant  these  form  a  correspondingly  large  percentage  of  carabid 
food,  the  increase  being  compensated  by  a  diminution  in  the  amount 
of  vegetable  food  taken.     (Forbes.)     Coccinellid  larvae  (excepting  Epi- 
lachna,  which  eats  leaves)  feed  almost  entirely  upon  plant  lice  and  con- 
stitute one  of  the  most  effective  checks  upon  their  multiplication;  the 
beetles  eat  aphides,  but  also  fungus  spores  and  pollen  in  large  quantities. 
Though  Lepidoptera  are  pre-eminently  phytophagous,   the  larva  of 
Feniseca  tarquinius  is  unique  in  feeding  solely  upon  plant  lice,  particular- 
ly the  woolly  Schizoneura  tessellata  of  the    alder.     Among  Diptera, 
Asilidae,  Midaidae,  There vidae  and  Empididae  are  the  chief  predaceous 
families.     Asilidae  (robber-flies)  ferociously  attack  not  only  other  flies, 
but  also  beetles,  bumblebees,  butterflies,  and  dragon  flies;  as  larvae 
they  feed  largely  upon  the  larvae  of  beetles.     Many  of  the  larvas  of 
Syrphidae  prey  upon  plant  lice,  and  the  larvae  of  Volucella  feed  in  Europe 
on  the  larvae  of  bumblebees  and  wasps.     Of  Hymenoptera,  the  ants  are 
to  a  great  extent  predaceous,  attacking  all  sorts  of  insects,  but  particu- 
larly soft-bodied  kinds;  while  Vespidae  feed  largely  upon  other  insects, 
though  like  the  ants  they  are  fond  of  the  nectar  of  flowers  and  the  juices 
of  fruits. 

Parasitic  Insects. — Though  very  many  insects  occur  as  external 
parasites  on  the  bodies  of  birds  and  mammals,  very  few  occur  as  such  on 


272 


ENTOMOLOGY 


the  bodies  of  other  insects;  one  of  the  few  is  Braula  ccBca,  a  wingless 
dipteron  found  on  the  body  of  the  honey  bee. 

A  vast  number  of  insects,  however,  undergo  their  larval  develop- 
ment as  internal  parasites  of  other  insects,  and  most  of  these  parasites 
belong  to  the  two  most  specialized  orders,  Diptera  and  Hymenoptera. 

The  larvae  of  Bombyliidae  feed  upon  the  eggs  of  Orthoptera  and  upon 
larv£e  of  Lepidoptera  and  Hymenoptera.  Tachinidae  are  the  most 
important  dipterous  parasites  of  other  insects  and  lay  their  eggs  most 
frequently  upon  caterpillars;  the  larvae  bore  into  their  victim,  develop 


Fig.  278. — Megarhyssa    atrata,    drilling    in    tree    trunk. 

Macnamara. 


Natural    size. — From  Charles 


within  its  body,  and  at  length  emerge  as  winged  insects.  These  parasites 
often  render  an  important  service  to  man  in  checking  the  increase  of 
noxious  Lepidoptera. 

The  great  majority  of  insect  parasites — many  thousand  species — 
belong  to  the  order  Hymenoptera,  constituting  one  of  the  primary 
divisions  of  the  order.  They  are  immensely  important  from  an  eco- 
nomic standpoint,  particularly  the  Ichneumonidae,  of  which  more  than 
ten  thousand  species  are  already  known.  Our  most  conspicuous 
ichneumonids  are  the  two  species  of  Megarhyssa,  M.  atrata  (Fig.  278), 
and  M.  lunator  with  their  long  ovipositors  (three  inches  long  in 
lunator,  and  four  to  four  and  three-quarters  inches  in  atrata) .  Mega- 
rhyssa bores  into  the  trunks  of  trees  in  order  to  reach  the  burrows  of 


INTERRELATIONS    OF    INSECTS 


273 


another  large  hymenopteron,   Tremex  columba  (Fig.  30),  upon  whose 
larvae  the  larva  of  Megarhyssa  feeds. 

The  enormous  family  Braconidoe,  closely  related  to  Ichneumonidae, 
is  illustrated  by  the  common  Apanteles  coiigregaius,  which  lays  its  eggs 
in  the  caterpillars  of  various  Sphingidae.  The  parasitic  larvae  feed  upon 
the  blood  and  possibly  also  the  fat-body  of  their  host,  and  at  length 
emerge  and  spin  their  cocoons  upon  the  exterior  of  the  caterpillar  (Fig. 
279),  sometimes  to  the  number  of  several  hundred.  Species  of  Aphidins 
transform  within  the  bodies  of  plant  lice,  one  to  each  host,  and  the  imago 
cuts  its  way  out  through  a  circular  opening  with  a  correspondingly 


Pig.   279. — A  tomato  worm,  Proloparce  sexla,  bearing  cocoons  of  the  parasitic  Apanteles 
congregatus.     Natural  size. 


circular  lid.  Chalcididae,  of  which  some  four  thousand  species  are 
known,  are  usually  minute  and  parasitic;  though  some  are  phytopha- 
gous, for  example,  species  of  Harmolita  (Isosoma)  which  live  in  wild  or 
cultivated  grasses,  and  the  clover  seed-midge  Bruchophagus  funebris. 
Chalcids  affect  a  great  variety  of  insects  of  one  stage  or  another,  such 
as  caterpillars,  pupas,  cockroach  eggs,  plant  lice  and  scale  insects; 
while  some  of  them  develop  in  cynipid  galls,  either  upon  the  larvae  of 
the  gall-makers  or  upon  the  larvae  of  inquilines.  Giard  in  France  reared 
more  than  three  thousand  chalcids  {Copidosoma  truncatellum)  from  a 
single  caterpillar  of  Plusia.  Proctotrypidae  are  remarkable  as  parasites. 
Most  of  them  are  minute;  indeed,  this  family  and  the  coleopterous  family 
Trichopterygidae  contain  the  smallest  winged  insects  known — species 
but  one-third  or  one-fourth  of  a  millimeter  long.     A  large  proportion 


274  ENTOMOLOGY 

of  the  Proctotrypidae  are  parasitic  in  the  eggs  of  other  insects  or  of 
spiders,  several  sometimes  developing  in  the  same  egg;  others  affect 
odonate  nymphs  and  coleopterous  or  dipterous  larvae,  while  several 
species  have  been  reared  from  itonidid  and  cynipid  galls,  and 
many  proctotrypids  are  parasites  of  other  parasitic  insects — in  other 
words,  are  hyper  parasites. 

Hyperparasitism. — Not  only  are  primary  parasites  frequently 
attacked  by  other,  or  secondary,  parasites,  but  tertiary  parasitism  is 
known  to  occur  in  a  few  instances,  and  there  is  some  reason  to  believe 
that  even  the  quaternary  type  exists  among  insects,  as  in  the  following 
case. 

The  caterpillar  of  Hemerocampa  leucostigma  defoliates  shade  trees 
in  the  northeastern  United  States.  An  enormous  increase  of  this 
species  in  the  city  of  Washington  in  1895  was  attended  by  a 
corresponding  increase  of  parasitic  and  predaceous  species,  and  this  unu- 
sual opportunity  for  the  study  of  parasitism  was  made  the  most  of  by 
Dr.  Howard,  from  whose  admirable  paper  these  facts  are  taken. 

The  primary  parasites  of  H.  leucostigma  numbered  23  species — 17 
Hymenoptera  and  6  Diptera;  of  the  hyperparasites  (all  hymenopterous) 
13  were  secondary,  2  and  probably  5  were  tertiary,  and  one  of  these 
(Asecodes  alhitarsis)  may  under  certain  conditions  prove  to  be  a  quater- 
nary parasite.  To  illustrate — The  ichneumon  Pimpla  inquisitor,  an 
important  primary  parasite  of  lepidopterous  larvas,  lays  its  eggs  in  cater- 
pillars of  H.  leucostigma;  its  larvae  suck  the  blood  of  their  host  and  at 
length  spin  their  cocoons  within  the  loose  cocoon  of  the  Hemerocampa. 
These  cocoons  have  yielded  a  well-known  secondary  parasite,  the  chalcid 
Dibrachys  houcheanus.  Now  another  chalcid,  Asecodes  alhitarsis,  has 
been  seen  to  issue  from  a  pupa  of  this  Dibrachys,  thus  establishing  terti- 
ary parasitism.  Furthermore,  it  is  quite  possible  that  Dibrachys 
itself  is  a  tertiary  parasite,  in  which  event  the  Asecodes  might  become 
a  parasite  of  the  quaternary  order. 

Economic  Importance  of  Parasitism. — If  a  primary  parasite  js 
beneficial,  its  own  parasites  are  indirectly  injurious,  generally  speaking; 
while  those  of  the  third  and  the  fourth  order  are  respectively  beneficial 
and  injurious.  The  last  two  kinds  are  so  rare,  however,  as  to  be  of  no 
practical  importance  from  an  economic  standpoint.  The  first  two  kinds 
are  of  immense  economic  importance,  particularly  the  primary  parasites. 
"  Outbreaks  of  injurious  insects,"  says  Howard,  "  are  frequently  stopped 
as  though  by  magic  by  the  work  of  insect  enemies  of  the  species.  Hub- 
bard found,  in  1880,  that  a  minute  parasite,  Tricho  gramma  pretiosa,  alone 


INTERRELATIONS    OF   INSECTS  275 

and  unaided,  almost  annihilated  the  fifth  brood  of  the  cotton  worm  in 
Florida,  fully  ninety  per  cent,  of  the  eggs  of  this  prolific  crop  enemy 
being  infested  by  the  parasite.  In  1895,  in  the  city  of  Washington, 
more  than  ninety-seven  per  cent,  of  the  caterpillars  of  one  of  our 
most  important  shade-tree  pests  [Hemerocampa,  as  just  mentioned] 
were  destroyed  by  parasitic  insects,  to  the  complete  relief  of  the  city  the 
following  year.  The  Hessian  fly,  that  destructive  enemy  to  wheat 
crops  in  the  United  States,  is  practically  unconsidered  by  the  wheat 
growers  of  certain  states,  for  the  reason  that  whenever  its  numbers 
begin  to  be  injuriously  great  its  parasites  increase  to  such  a  degree  as  to 
prevent  appreciable  damage. 

"The  control  of  a  plant-feeding  insect  by  its  insect  enemies  is  an  ex- 
tremely complicated  matter,  since,  as  we  have  already  hinted,  the 
parasites  of  the  parasites  play  an  important  part.  The  undue  multipli- 
cation of  a  vegetable  feeder  is  followed  by  the  undue  multiplication  of 
parasites,  and  their  increase  is  followed  by  the  increase  of 
hyperparasites.  Following  the  very  instance  of  the  multiplication  of 
the  shade  tree  caterpillar  just  mentioned,  the  writer  [Howard]  was  able 
to  determine  this  parasitic  chain  during  the  next  season  down  to  quater- 
nary parasitism.  Beyond  this  point,  true  internal  parasitism  probably 
did  not  exist,  but  even  these  quaternary  parasites  were  subject  to 
bacterial  or  fungus  disease  and  to  the  attacks  of  predatory  insects. 

*'The  prime  cause  of  the  abundance  or  scarcity  of  a  leaf-feeding 
species  is,  therefore,  obscure,  since  it  is  hindered  by  an  abundance  of 
primary  parasites,  favored  by  an  abundance  of  secondary  parasites 
(since  these  will  destroy  the  primary  parasites),  hindered  again  by  an 
abundance  of  tertiary  parasites,  and  favored  again  by  an  abundance  of 
quaternary  parasites." 

Entomologists  have  made  many  attempts  to  import  and  propagate 
insect  enemies  of  various  introduced  insect  pests,  and  some  of  their 
efforts  have  been  crowned  with  success,  as  was  notably  the  case  when 
Novius  cardinalis,  a  lady-bird  beetle,  was  taken  from  Australia  to  Cali- 
fornia to  destroy  the  fluted  scale. 

Form  of  Parasitic  Larvae. — The  peculiar  environment  of  parasitic 
larvae  is  responsible  for  profound  changes  in  their  organization.  These 
larvae,  in  general,  are  apodous,  the  body  is  compact  and  the  head  is  more 
or  less  reduced,  sometimes  to  the  merest  rudiment.  These  characters, 
occurring  also  in  such  dipterous  larvae  as  Hve  in  a  mass  of  decaying  or- 
ganic matter,  and  again  in  those  hymenopterous  larvae  whose  food  is  pro- 
vided by  the  mother  or  by  nurses,  are  to  be  attributed  to  the  presence 


276  ENTOMOLOGY 

of  a  plentiful  supply  of  food,  obtainable  with  little  or  no  exertion,  and 
indicate,  not  primitive  simplicity  of  organization,  but  a  high  degree  of 
speciahzation,  as  we  have  said  before.  The  embryonic  development  of 
parasitic  larvae  is  frequently  highly  anomalous,  as  appears  in  the  chapter 
on  development. 

Maternal  Provision. — Excepting  several  families  of  Hymenoptera 
and  the  Termitidae,  few  insects  make  any  special  provision  for  the  wel- 
fare of  the  young  beyond  laying  the  eggs  in  some  appropriate  situation. 
Many  insects,  as  walking-sticks  (Phasmidae)  and  some  butterflies 
{Argynnis)  simply  drop  their  eggs  to  the  ground,  leaving  the  young  to 
shift  for  themselves.  Most  insects,  however,  instinctively  lay  their 
eggs  in  situations  where  the  larva  is  sure  to  find  its  proper  food  near  at 
hand.  Thus  various  flies  and  beetles  deposit  their  eggs  on  decaying 
animal  matter,  butterflies  and  moths  are  more  or  less  restricted  to  par- 
ticular species  of  plants,  and  parasitic  Hymenoptera  to  certain  species  of 
insects.  The  beetles  of  the  genus  Necrophorus  go  so  far  as  to  bury  the 
body  of  a  bird,  mouse  or  other  animal  in  which  the  eggs  are  to  be  laid; 
and  in  this  instance  the  male  assists  the  female  in  undermining  and 
afterward  covering  the  body.  A  similar  co-operation  of  the  two  sexes 
occurs  in  the  scarabaeid  beetles  known  as  "tumblebugs,"  a  pair  of  which 
may  often  be  seen  rolling  along  laboriously  a  ball  of  dung  which  is  to 
serve  as  larval  food.  The  female  mole-cricket  {Gryllotalpa)  is  said  to 
care  for  her  eggs  and  even  to  feed  the  young  at  first. 

Hymenoptera  display  all  degrees  of  complexity  in  regard  to  maternal 
provision.  Tenthredinidae  simply  lay  their  eggs  on  the  proper  food 
plants  or  else  insert  them  into  the  tissues  of  the  plants.  Sphecina  make 
a  nest,  provision  it  with  food  and  leave  the  young  to  care  for  themselves. 
Queen  wasps  and  bumblebees  go  a  step  further  in  feeding  the  first  larvae 
and  carrying  them  to  maturity.  Finally,  in  the  honey  bee  the  care  of 
the  young  is  at  once  relegated  by  the  queen  to  other  individuals  of  the 
colony,  as  is  also  the  case  among  ants. 

Some  of  the  most  elaborate  examples  of  purely  maternal  provision 
are  found  among  the  digger  wasps  and  the  solitary  wasps;  these  in- 
stances are  highly  interesting,  involving  as  they  do  an  intricate  co-ordi- 
nation of  many  reflex  actions — as  appears  in  the  discussion  of  insect 
behavior. 

Among  the  Sphecina,  or  digger  wasps,  the  female  makes  a  nest  by 
burrowing  into  the  ground,  by  mining  into  such  pithy  plants  as  elder  or 
sumach,  or  else  by  plastering  bits  of  mud  together.  The  nest  is  provi- 
sioned with  insects  or  spiders  which  have  been  stung  in  such  a  way  as 


INTERRELATIONS    OF    INSECTS  277 

usually  to  be  paralyzed,  without  being  actually  killed.  The  various 
species  of  Sphecina  frequently  select  particular  species  of  insects  or 
spiders  as  food  for  the  young.  Pepsis  Jormosa  (Pompilidaj)  uses  taran- 
tulas for  this  purpose;  Sphecius  speciosus  (Bembecidie)  stores  her  nest 
with  a  cicada;  Nyssonidae  pick  out  certain  species  of  Membracidae ; 
mud-daubers  (Sphecidae)  use  spiders;  and  other  families  of  Sphecina 
capture  bees,  beetles,  plant  lice  or  other  insects,  as  the  case  may  be. 
The  solitary  wasps  (Eumenidae)  are  similar  to  the  digger  wasps  in  habits. 

Of  the  solitary  bees,  Megachile  is  well  known  for  its  habit  of  cutting 
pieces  out  of  rose  leaves;  it  uses  oblong  pieces  to  form  a  thimble-shaped 
tube  which,  after  being  stored  with  pollen  and  nectar,  is  plugged  with  a 
circular  piece  of  leaf.  The  larval  cells  are  made  either  in  tunnels  ex- 
cavated in  wood  by  the  mother  or  else  in  cracks  or  other  chance  cavities. 

One  of  the  carpenter  bees,  Ceratina  dupla,  which  builds  in  the  hollow 
stem  of  a  plant  a  series  of  larval  cells  separated  by  partitions,  is  said  by 
Comstock  to  watch  over  her  nest  until  the  young  mature. 

The  transition  from  the  solitary  to  the  social  habit  is  indicated  in  the 
lifq-histories  of  wasps  and  bumblebees,  where  a  solitary  queen  founds 
the  colony  but  soon  relegates  to  other  individuals  all  duties  except  that 
of  egg-laying.     The  social  insects  will  now  be  considered. 

Termites 

Though  popularly  known  as  "white  ants,"  the  termites  are  quite 
different  from  true  ants,  being  indeed  not  very  far  removed  from  the 
most  primitive  insects.  In  view  of  the  extreme  contrast  in  structure 
and  development  between  termites  and  ants,  it  is  remarkable  that  the 
two  groups  should  have  much  the  same  kind  of  complex  social 
organization. 

Classes  of  Termites.^ — In  general,  four  principal  kinds  of  adults  are 
produced  in  a  community  of  termites,  namely — workers,  soldiers,  fertile 
males  and  fertile  females. 

The  workers  (Fig.  280,  A)  which  are  ordinarily  the  most  numerous,- 
are  of  either  sex,  but  their  reproductive  organs  are  undeveloped.  A 
worker  ant  or  .bee,  is,  however,  always  a  female.  The  termite  workers, 
as  the  name  impHes,  do  most  of  the  work;  they  make  the  nest,  provide 
food,  feed  and  care  for  the  young  and  the  royal  pair,  and  attend  to 
many  other  domestic  duties. 

The  soldiers,  like  the  workers,  are  of  either  sex,  with  undeveloped 
sexual  organs.     With  monstrous  mandibles  and  head  (Fig.  280,  B), 


278 


ENTOMOLOGY 


their  chief  duty  apparently  is  to  defend  the  colony,  though  they  fre- 
quently fail  to  do  so. 

The  winged  males. and  females  (Fig.  280,  C)  which  are  sexually  ma- 


FiG.  280. — Various  forms  of  Reticulitermes  lucifugus.  A,  adult  worker;  B,  soldier;  C, 
perfect  winged  insect;  D,  perfect  insect  after  shedding  the  wings;  E,  young  complementary 
queen;  F,  older  complementary  queen.     Enlarged. — After  Grassi  and  Sandi.^s. 


ture,  swarm  from  the  nest  and  mate.  After  the  nuptial  flight  the  pair 
burrow  into  some  crevice  and  shed  the  wings,  which  break  off  each  along 
a  peculiar  transverse  suture,  leaving  four  triangular 
stumps  (Fig.  280,  D).  The  king  and  queen  found 
a  new  colony  and  may  live  for  several  years,  shelt- 
ered in  a  special  chamber;  the  queen,  meanwhile, 
becoming  enormously  distended  (Fig.  281)  with  eggs 
and  almost  incapable  of  locomotion.  The  prolificacy 
of  the  queen  is  astonishing;  she  can  lay  thousands 
of  eggs,  sometimes  at  the  rate  of  sixty  per  minute. 
She  is  the  nucleus  of  the  colony,  and  should  she 
become  incapacitated,  is  replaced  by  one  or  more 
substitute  queens,  which  have  been  developed  to 
meet  the  emergency;  similarly,  a  substitute  king  is 
matured  upon  occasion.  These  substitutes  (Fig. 
280,  E)  differ  from  the  primary  pair  in  having 
nymphal  wing  pads  in  place  of  the  remains  of  func- 
tional wings. 

In  regard  to  Termopsis  angusticollis,  in  California, 
Dr.  Heath  says  that  if  only  one  of  the  royal  pair  be 
destroyed   usually   only    one    substitution    form    is 
developed,  but  when  both  perish,  from  ten  to  forty 
substitutes  appear,  according  to  the  size  of  the  colony. 

In  all,  three  types  of  reproductive  forms  are  recognized :  ^r^/  form, 


Fig.  281. — Queen 
of  Termes  obesus. 
Natural  size. — After 
Hagen. 


INTERRELATIONS    OF   INSECTS  279 

true  kings  and  queens,  with  functional  wings  or  their  remnants;  second 
form,  substitute  males  or  females,  with  short  wing  pads;  third  form, 
ergatoid,  or  worker-like,  males  or  females,  without  wings,  this  type 
being  rather  rare. 

In  certain  tropical  species  there  are  two  types  of  soldiers,  and  two  of 
workers;  so  that  adults  of  either  sex  may  occur  under  seven  different 
forms  in  the  same  colony. 

Origin  of  Castes. — Grassi  maintains  that  all  the  forms  are  ahke  at 
birth  except  as  regards  sex,  and  that  the  differences  between  worker 
and  soldier,  which  are  independent  of  sex,  depend  probably  upon  nutri- 
tion. Grassi  attributes  all  the  diversities  of  caste,  except  the  sexual 
ones,  to  the  character  and  amount  of  the  food. 

C.  B.  Thompson  states  that  at  hatching  there  are  two  kinds  of 
nymphs  (i)  the  "reproductive,"  which  develop  into  the  fertile  castes, 
and  (2)  the  ''worker-soldier"  nymphs,  which  become  the  sterile  castes; 
these  two  types  being  distinguishable  by  internal  differences  in  the  brain, 
compound  eyes,  and  sex  organs. 

Food.— The  food  of  termites  is  of  six  kinds:  (i)  wood;  (2)  matter 
emitted  from  the  oesophagus  or  rectum,  termed  respectively  stomodasal 
and  proctodaeal  food;  (3)  cast  skins  and  other  exuvialstuflf ;  (4)  the  bodies 
of  their  companions;  (5)  saliva;  (6)  water.  Of  these  the  proctodaeal 
food  is  the  favorite.  Nymphs  receive  at  first  only  saliva;  later  they  get 
stomod^eal  and  proctodaeal  food  until,  finally,  they  are  able  to  eat  wood 
— the  staple  food  of  a  termite. 

American  Species. — Our  common  termite  is  Reticulitermes  jiavipes, 
which  occurs  throughout  the  United  States,  excavating  its  galleries  in 
decaying  logs,  stumps  or  other  dead  wood.  The  nuptial  flight  of  this 
species  takes  place  in  spring,  when  the  two  sexes  swarm  in  numbers  that 
are  sometimes  enormous.  One  swarm,  as  recorded  by  Hagen,  appeared 
as  a  dense  cloud,  and  was  being  followed  and  attacked  by  no  less  than 
fifteen  species  of  birds,  among  which  were  robins,  bluebirds  and  sparrows; 
some  of  the  robins  were  so  gorged  to  the  mouth  with  termites  that  their 
beaks  stood  open.  Though  plenty  of  winged  females  are  said  to  occur 
in  the  swarming  season,  the  true  queen  of  R.  fiavipes  is  extremely  rare, 
the  queen  usually  found  being  evidently,  from  her  undeveloped  wings, 
a  substitute  queen. 

The  European  species  Reticulitermes  lucifugus  has  been  found 
recently  in  Massachusetts.  Most  species  of  termites  occur  in  warm 
climates,  however.     North  of  Mexico  thirty-six  species  are  known, 


28o 


ENTOMOLOGY 


most  of  which  have  come  from  the  south,  and  more  species  are  liable  to 
be  introduced  at  any  time  (Banks). 

Architecture. — While  many  termites  simply  burrow  in  dead  wood, 
other  species  construct  more  elaborate  nests.  A  Jamaican  species 
builds  huge  nests  in  the  forks  of  trees,  with  covered  passageways  leading 
to^the  ground. 

In  parts  of  Africa  and  Australia,  where  they  are  free  from  disturbance, 


Fig.  282. — Termite  mound,  Kimber- 
ley  type,  Australia. — After  Saville- 
Kent. 


Fig.  2S3. — Mound  of  the  "com- 
pass" termite  of  North  Australia. — 
After  Saville-Kent. 


termites  erect  huge  mounds,  frequently  six  to  ten  and  sometimes 
eighteen  or  twenty  feet  high,  with  galleries  extending  as  far  below  the 
surface  of  the  ground  as  they  do  above  it.  These  immense  structures 
(Fig.  282)  consist  chiefly  of  earth,  cemented  by  means  of  some  secretion 
into  a  stony  clay,  with  which  also  much  excrementitious  matter  is  mixed ; 
they  are  pyramidal,  columnar,  pinnacled  or  of  various  other  forms,  ac- 
cording to  the  species,  and  are  perforated  by  thousands  of  passages  and 
chambers,  while  there  are  underground  galleries  extending  away  from 
the  mound  to  a  distance  of  often  several  hundred  feet. 


INTERRELATIONS    OF    INSECTS  201 

An  extraordinary  type  of  mound  is  constructed  by  the  "compass" 
or  "meridian,"  termites  of  North  Australia,  for  their  wedge-shaped 
mounds  (Fig.  283),  commonly  eight  or  ten  feet  high,  though  sometimes 
as  high  as  twenty  feet,  are  directed  north  and  south  with  surprising  accu- 
racy. By  means  of  this  orientation  the  exposure  to  the  heat  of  the  sun  is 
reduced  to  the  minimum,  as  occurs  also  in  the  case  of  many  Austrahan 
plants,  the  leaves  of  which  present  their  edges  instead  of  their  faces  to 
the  sun. 

More  than  one  species  of  termite  may  inhabit  a  single  nest;  in  one 
South  African  nest  Haviland  found  live  species  of  termites  and  three  of 
ants.  The  widely  distributed  genus  Eutermes  is  essentially  a  group  of 
inquiline,  or  guest,  species.  Termite  mounds  afford  shelter  to  scor- 
pions, snakes,  lizards,  rats,  and -even  birds,  some  of  which  nest  in  them. 
The  Australian  bushmen  hollow  out  the  mounds  to  make  temporary 
ovens,  and  even  eat  the  clay  of  which  they  are  composed,  while  hill- 
tribes  of  India  are  accustomed  to  eat  the  termites  themselves,  the 
flavor  of  which  is  said  to  be  delicious. 

Ravages. — In  tropical  regions  the  amount  of  destruction  done  by 
termites  is  enormous,  and  these  formidable  pests  are  a  constant  source 
of  consternation  and  dread.  They  emit  a  secretion  that  corrodes 
metals  and  even  glass,  while  anything  made  of  wood  is  simply  at  their 
mercy.  Always  avoiding  the  light,  they  hollow  out  floors,  rafters  or 
furniture,  leaving  only  a  thin  outer  shell,  and  as  a  result  of  their  in- 
sidious work  a  chair  or  a  table  may  unexpectedly  crumble  at  a  touch. 
Jamestown,  the  capital  of  St.  Helena,  was  largely  destroyed  by  termites* 
(1870)  and  had  to  be  rebuilt  on  that  account. 

In  the  United  States  and  Europe  few  species  of  termites  occur,  and 
they  do  little  injury  as  compared  with  the  tropical  species;  though  our 
common  Reticulitermes  flavipes  occasionally  damages  woodwork,  books, 
plants,  etc.,  in  an  extensive  way,  particularly  in  the  Southern  states. 

Termitophilism. — Associating  with  termites  are  found  various 
other  arthropods,  mostly  insects.  The  relations  of  these  termitophilous 
forms  to  the  termites  are,  so  far  as  is  known,  similar  to  those  described 
beyond  between  myrmecophilous  species  and  ants. 

Honey  Bee 

For  more  than  three  thousand  years  the  honey  bee  has  been  almost 
unique  among  insects  as  an  object  of  human  care  and  study.  It  was 
highly  prized  by  the  old  Greeks  and  Romans  (as  appears  from  the  writ- 


282 


ENTOMOLOGY 


ings  of  Aristotle,  330  B.  C,  and  Cato,  about  200  B.  C.)  and  actually 
worshiped  as  a  symbol  of  royalty  by  the  ancient  Egyptians,  through 
whose  papyri  and  scarabs  the  honey  bee  may  be  traced  back  to  the  time 
of  Rameses  I.,  or  1400  B.  C. 

The  honey  bee,  unhke  domesticated  animals,  is  so  little  dependent 
upon  man  that  it  readily  returns  to  a  wild  hfe.  Under  many  dis- 
tinct races,  which  are  due  largely  to  human  intervention.  Apis  niel- 
lifera  is  widely  distributed  over  the  earth. 

Castes.— The  species  comprises  three  kinds  of  individuals:  queen, 
drone  and  worker  (Fig.  284) .  The  workers  are  females  with  an  atrophied 
reproductive  system.  They  constitute  the  vast  majority  in  any  colony 
and  are  the  only  kind  that  is  commonly  seen  out  of  doors.  Upon  the 
industrious  workers  falls  the  burden  of  the  labor;  they  build  the  comb, 


Fig.  2f 


A  B  C 

-The  honey  bee,  Apis  mellifera.     A,  queen;  B,  drone;  C,  worker.      Natural  size. 


nurse  the  young,  gather  foCd,  clean  and  repair  the  nest,  guard  it  from 
intruders,  control  larval  development,  expel  the  drones — briefly,  the 
workers  alone  are  responsible  for  the  general  management  of  the  com- 
munity. Though  hibernating  workers  Hve  eight  or  nine  months,  the 
other  workers  live  but  from  five  to  twelve  weeks. 

The  term  queen  is,  of  course,  a  misnomer,  for  the  government  of 
the  hive  is  anything  but  monarchical.  The  chief  duties  of  the  queen, 
or  mother,  are  simply  to  lay  eggs  and  to  lead  away  a  swarm.  She  is  able 
to  deposit  as  many  as  4,000  eggs  in  twenty-four  hours.  After  a  single 
mating,  the  spermatozoa  retain  their  vitality  in  the  spermatheca  of  the 
queen  for  three  or  four  years — the  lifetime  of  a  queen.  The  males,  or 
drones,  apart  from  their  occasional  sexual  usefulness,  are  of  little  or  no 
service,  and  their  very  name  has  become  an  expression  for  laziness. 

The  Comb. — Wax,  of  which  the  comb  is  built,  is  made  from  honey  or 
sugar,  many  pounds  (twenty,  according  to  Huber)  of  honey  being  re- 
quired to  make  one  pound  of  wax.  The  workers,  gorged  with  nectar, 
cling  to  one  another  in  a  dense  heated  mass  until  the  white  films  of  wax 


INTERRELATIONS    OF    INSECTS 


>83 


appear  underneath  the  abdomen  (Fig.. 104) ;  these  are  transferred  to  the 
mouth,  as  described  on  page  229,  and  are  masticated  with  a  fluid, 
secreted  by  cephalic  glands,  which  alters  the  chemical  composition  of 
the  wax  and  makes  it  plastic. 

The  workers  now  contribute  their  wax  to  form  a  vertical,  hanging 
septum,  on  the  opposite  sides  of  which  they  proceed  to  bite  out  pits — 

the  bottoms   of    the   future    cells — using   the  

excavated  wax  in  making  the  cell  walls.  The 
bottom  of  each  cell  consists  of  three  rhombic 
plates  (Fig.  285,  A),  and  the  cells  of  one  side 
interdigitate  with  those  of  the  other  side  (Fig. 
285,  B)  in  such  a  way  that  each  rhomb  serves 
for  two  cells  at  once.  Wax  is  such  a  precious 
substance  that  it  is  used  (instinctively,  how- 
ever) always  with  the  greatest  economy;  the 
cell  walls,  are  scraped  to  a  thinness  of  3-^80  or 
}ioo  of  an  inch,  and  nowhere  is  more  wax  used 
than  is  suflBcient  for  strength;  one  pound  of  wax 
makes  from  35,000  to  50,000  worker  cells.  The 
cells,  at  first  circular  in  cross  section,  become 
hexagonal  from  the  mutual  interference  of 
workers  on  opposite  sides  of  the  same  wall; 
the  form  is,  however,  by  no  means  a  regular 
hexagon  in  the  mathematical  sense,  for  it  is  difficult  to  find  a  cell  with 
errors  of  less  than  3  or  4  degrees  in  its  angles.  (Cheshire.)  Worker 
cells  are  one  fifth  of  an  inch  in  diameter,  while  the  larger  cells,  destined 
for  drones  or  to  hold  honey,  are  one  quarter  of  an  inch  across. 

To  strengthen  the  edges  of  cells  or  to  fill  crevices,  the  workers  use 
propolis,  the  sticky  exudation  from  the  buds  or  leaf  axils  of  poplar,  fir, 
horse-chestnut  or  other  trees;  though  they  will  utilize  instead  such  arti- 
ficial substances  as  grease,  pitch  or  varnish.  As  winter  approaches,  the 
bees  apply  the  propolis  liberally,  making  their  abode  tight  and 
comfortable. 

Larval  Development. — When  the  brood  cells  are  ready,  the  queen, 
attended  by  workers,  lays  an  egg  in  each  cell  and  has  no  further  con- 
cern as  to  its  fate.  After  three  days  the  egg  discloses  a  footless  grub 
(Figs.  286,  287)  which  depends  at  first  upon  the  milky  food  that  bathes 
it  and  has  been  supplied  from  the  mouths  of  the  worker  nurses.  Later 
the  larva  is  weaned  by  its  nurses  to  pollen,  honey  and  water.  As  the 
stomach  and  the  intestine  of  the  larva  do  not  communicate  with  each 


Fig.  285. — A,  bases  of 
comb  cells;  B,  section  of 
comb.  Somewhat  e  n- 
larged. — After  Cheshire. 


284 


ENTOMOLOGY 


Other,  the  excretions  of  the  larva  cannot  contaminate  the  surrounding 
nutriment,   and   are  retained  until    the  final   molt.     Five  days  after 

hatching,  the  larva  spins  its  cocoon, 
the  workers  having  meanwhile  cov- 
ered the  larval  cells  with  a  porous 
cap  of  wax  and  pollen  (Fig.  287) 
and  on  the  twenty-first  day  after 
the  egg  was  laid  the  winged  worker 
bee  cuts  its  way  out,  assisted  in 
this  operation  by  the  ever-attentive 
nurses.  Now,  after  acquiring  the 
use  of  its  faculties,  the  newly 
emerged  bee  itself  assumes  the 
duties  of  a  nurse,  but  as  soon  as 
its  cephalic  nursing  glands  are 
exhausted  it  becomes  a  forager. 
This  account  applies  to  the  worker; 
the  three  kinds  of  individuals  differ 
Fig.  286.— Comb  of  honey  bee,  showing  in  respect  to  the  number  of  days 
the  insect  in  various  stages.    At  the  right    required    for    development,    as 

are  large  queen  cells. — After  Benton.  ^  _  '^  ' 

appears    in    the    following    table, 
from  Phillips: 


Queen. . 
Worker. 
Drone.  . 


Egg. 

Larva. 

Pupa. 

Total 

3 

s'A 

jH 

16 

3 

6 

12 

21 

3 

6}^ 

I4>2 

24 

The  cells  in  which  queens  develop  (Fig.  286)  are  quite  different  from 
worker  or  drone  cells,  being  much  larger,  more  or  less  irregular  in  form, 
and    vertical     instead     of 

horizontal;    they    are  ^^l  P 

attached  usually  to  the 
lower  edge  of  a  comb  or 
else  to  one  of  the  side 
edges. 

Other  Facts.— The 
entire  organization  of  the 
honey  bee  has  been  pro- 
foundly modified  with  ref- 
erence to  floral  structure;  the  life  of  the  bee  is  wrapped  up  in  that  of 
the  flower.     The  more  important  structural   adaptations   of  bees  in 


Fig.   287. — Honey   bee.     /,    feeding    larva;    p,    pupa; 
s,  spinning  larva. — After  Cheshire. 


INTERRELATIONS    OF    INSECTS  285 

relation  to  flowers  have  been  described,  as  well  as  many  of  their  sensory 
peculiarities;  there  remain  to  be  added,  however,  some  other  items  of 
interest,  chosen  from  the  many. 

A  colony  of  bees  in  good  condition  at  the  opening  of  the  season  con- 
tains a  laying  queen  and  some  30,000  to  40,000  worker  bees,  or  six  to 
eight  quarts  by  measurement.  Besides  this  there  should  be  four,  five, 
or  even  more  combs  fairly  stocked  with  developing  brood,  with  a  good 
supply  of  honey  about  it.  Drones  may  also  be  present,  even  to  the 
number  of  several  hundred. 

Ordinarily  the  queen  mates  but  once,  flying  from  the  hive  to  meet 
the  drone  high  in  the  air,  when  five  to  nine  days  old  usually.  Seminal 
fluid  sufficient  to  impregnate  the  greater  number  of  eggs  she  will  deposit 
during  the  next  two  or  three  years  (sometimes  even  four  or  five  years) 
is  stored  at  the  time  of  mating  in  a  sac— the  spermatheca,  opening  into 
the  egg-passage. 

The  liquid  secreted  in  the  nectaries  of  flowers  is  usually  quite  thin, 
containing,  when  just  gathered,  a  large  percentage  of  water.  Bees  suck 
or  lap  it  up  from  such  flowers  as  they  can  reach  with  their  flexible,  suck- 
ing tongue,  0.25  to  0.28  inch  long.  This  nectar  is  taken  into  the  honey 
sac,  located  in  the  abdomen,  for  transportation  to  the  hive.  Besides 
being  thin,  the  nectar  has  at  first  a  raw,  rank  taste,  usually  the  flavor 
and  odor  peculiar  to  the  plant  from  which  gathered,  and  these  are  fre- 
quently far  from  agreeable.  To  make  from  this  raw  product  the  health- 
ful and  delicious  table  luxury  which  honey  constitutes — "fit  food  for  the 
gods" — is  another  of  the  functions  peculiar  to  the  worker  bee.  The 
first  step  is  the  stationing  of  workers  in  lines  near  the  hive  entrances. 
These,  by  incessant  buzzing  of  their  wings,  drive  currents  of  air  into  and 
out  of  the  hive  and  over  the  comb  surfaces.  If  the  hand  be  held  before 
the  entrance  at  such  a  time  a  strong  current  of  warm  air  may  be  felt 
coming  out.  The  loud  buzzing  heard  at  night  during  the  summer  time 
is  due  to  the  wings  of  workers  engaged  chiefly  in  ripening  nectar.  In- 
stead of  being  at  rest,  as  many  suppose,  the  busy  workers  are  caring  for 
the  last-gathered  lot  of  nectar  and  making  room  for  further  accessions. 
This  may  go  on  far  into  the  night,  or  even  all  night,  to  a  greater  or  less 
extent,  the  loudness  and  activity  being  proportionate  to  the  amount  and 
thinness  of  the  liquid.  Frequently  the  ripening  honey  is  removed  from 
one  set  of  cells  and  placed  in  others.  This  may  be  to  gain  the  use  of 
certain  combs  for  the  queen,  or  possibly  it  is  merely  incidental  to  the 
manipulation  the  bees  wish  to  give  it.  When,  finally,  the  process  has 
been  completed,  it  is  found  that  the  water  content  has  usually  been  re- 


286  ENTOMOLOGY 

duced  to  lo  or  12  per  cent.,  and  that  the  disagreeable  odors  and  flavors, 
probably  due  to  volatile  oils,  have  also  been  driven  off  in  a  great  measure, 
if  not  wholly,  by  the  heat  of  the  hive,  largely  generated  by  the  bees. 
During  the  manipulation  an  antiseptic  (formic  acid) ,  secreted  by  glands 
in  the  head  of  the  bee,  and  possibly  other  glandular  secretions  as  well 
have  been  added.  The  finished  product  is  stored  in  waxen  cells  above 
and  around  the  brood  nest  and  the  main  cluster  of  bees,  as  far  from  the 
entrance  as  it  can  be  and  still  be  near  to  the  brood  and  bees.  The  work 
of  sealing  with  waxen  caps  then  goes  forward  rapidly,  the  covering  being 
more  or  less  porous.  Each  kind  of  honey  has  its  distinctive  flavor  and 
aroma,  derived,  as  already  indicated,  mainly  from  the  particular  blos- 
soms by  which  it  was  secreted,  but  modified  and  softened  by  the 
manipulation  given  it  in  the  hives.  The  last  three  paragraphs  are  taken 
from  Benton's  useful  manual. 

The  phenomenon  of  "swarming"  results  from  the  tremendous  re- 
productive capacity  of  the  queen,  though  it  is  immediately  an  instance 
of  positive  phatotropism,  as  Kellogg  has  shown.  Accompanied  by  most  of 
the  workers,  the  old  queen  abandons  the  hive  to  establish  a  new  colony. 
The  workers  that  remain  behind  have  provided  against  this  contingency, 
however,  and  the  departed  queen  is  soon  replaced  by  a  new  one. 

Determination  of  Caste.- — The  difference  between  queen  and  worker 
depends  solely  upon  nutrition,  both  forms  being  derived  from  precisely 
the  same  kind  of  egg.  To  produce  a  queen,  a  large  cell  of  special  form 
is  constructed,  and  its  occupant,  instead  of  being  weaned,  is  fed  almost 
entirely  upon  the  highly  nutritious  secretion  which  worker  grubs  receive 
only  at  first  and  in  limited  quantity.  This  nitrogenous  food,  the  prod- 
uct of  cephalic  glands,  develops  the  reproductive  system  in  proportion 
to  the  amount  received.  Drone  larvae  get  much  of  it,  though  not  so 
much  as  queens,  while  an  occasional  excess  of  this  "royal  jelly"  is 
beheved  to  account  for  the  abnormal  appearance  of  fertile  workers. 

Parthenogenesis,  or  reproduction  without  fertilization,  is  known  to 
occur  in  the  bee,  as  well  as  in  various  other  insects.  The  always  un- 
fertilized eggs  of  workers  produce  invariably  drones,  as  do  also  unfertil- 
ized eggs  of  the  queen. 

Dzierzon's  Theory. — The  much  discussed  theory  of  Dzierzon,  pro- 
posed more  than  seventy-five  years  ago,  is  essentially  as  follows:  (i) 
the  queen  is  able  "at  will"  to  lay  either  male  or  female  eggs;  (2)  all 
the  eggs  in  the  ovaries  would  develop  into  males  if  unfertihzed,  but 
fertihzed  eggs  produce  females. 

It  is  a  matter  of  common  observation  that  the  queen  is  able  to  lay 


INTERRELATIONS    OF   INSECTS  287 

female  eggs  in  worker  or  queen  cells,  and  male  eggs  in  drone  cells;  but 
the  means  by  which  she  exercises  control  over  the  fertilization  of  the 
eggs  is  not  understood. 

It  is  known  that  unfertilized  eggs  produce  always  drones,  and  at 
present  it  is  generally  beheved  by  geneticists  that  drones  never 
come  from  fertilized  eggs.  The  principal  reasons  for  this  opinion 
are  these:  (i)  if  a  pure-bred  queen  of  one  race  is  crossed  with  a  drone 
of  another  race,  the  female  progeny  (workers  or  queens)  have  hybrid 
characters,  but  the  male  offspring  have  only  characters  of  the  maternal 
race;  (2)  eggs  from  worker  or  queen  cells  contain  spermatozoa;  those 
from  drone  cells  do  not. 

Bumblebees 

Familiar  as  the  bumblebees  are,  their  habits  have  been  little  studied 
in  this  country,  though  in  England  ''bumblebees"  have  formed  the 
subject  of  an  interesting  volume  by  Sladen.  The  queen  hibernates  and 
in  spring  starts  a  colony,  utilizing  frequently  for  this  purpose  the 
deserted  nest  of  a  field  mouse  or  sometimes  the  burrow  of  a  mole  or 
gopher.  The  queen  lays  her  eggs  in  a  small  mass  of  pollen  mixed  with 
nectar  (Putnam) .  The  larvae  eat  out  cavities  in  the  mass  of  food  and 
when  full  grown  spin  silken  cocoons,  from  which  the  imago  cuts  its 
way  out;  the  empty  cocoon  being  subsequently  used  as  a  receptacle  for 
honey.  At  first  only  workers  are  produced  and  they  at  once  relieve  the 
queen  of  the  duties  of  collecting  nectar  and  pollen,  caring  for  the  young, 
etc.  The  workers  are  of  different  sizes,  the  smaller  ones  being  nurses 
or  builders  and  the  larger  ones  foragers — the  kind  commonly  seen  out  of 
doors.  In  the  latter  part  of  summer  both  males  and  females  are  pro- 
duced, but  when  severe  frost  arrives,  the  old  queen,  the  workers  and  the 
males  succumb,  leaving  only  the  young  queens  to  survive  the  winter. 

Social  Wasps 

The  Social  Wasps  constitute  the  family  Vespidas,  of  which  we  have 
three  genera,  namely,  Vespa,  Polistes  and  Polybia,  the  last  genus  being 
represented  by  a  single  Californian  species. 

Vespa.— Some  species  of  Vespa,  as  V.  maculata,  make  a  nest  which 
consists  of  several  tiers  of  cells  protected  by  an  envelope  (Fig.  288),  at- 
taching the  nest  frequently  to  a  tree;  other  species,  as  germanica  and 
vulgaris,  make  a  nest  underground.     The  paper  of  which  the  nests  are 


288  ENTOMOLOGY 

composed  is  manufactured  from  weather-worn  shreds  of  wood,  which 
are  torn  off  by  the  mandibles  and  then  masticated  with  a  secreted  fluid 
which  cements  the  paper  and  makes  it  waterproof. 

A  solitary  queen  founds  the  colony  in  spring;  she  starts  the  nest, 
lays  eggs,  feeds  the  young  and  brings  forth  the  first  workers;  these  then 
relieve  her — continue  the  building  operations,  collect  food,  nurse  the 
young;  in  short,  assume  the  burden  of  the  labor.  In  the  latter  part  of 
summer,  fertile  males  and  females  appear  and  pairing  occurs.  Though 
the  statement  has  often  been  made  that  only  the  young  queens  survive 


^^ 


Fig.  288. — Nest  of  wasp,  Vespa  macidata.     A,  outer  aspect;  B,  with  envelope  cut  away  to 
show   combs.     Greatly  reduced. 


the  winter,  there  is  some  reason  to  believe  that  not  only  the  queens  but 
also  males  and  workers  may  hibernate  successfully  in  the  nest. 

The  larvae  are  fed  at  first,  by  regurgitation,  upon  the  sugary  nectar 
of  flowers  and  the  juices  of  fruits,  and  later  upon  more  substantial  food, 
such  as  the  softer  parts  of  caterpillars,  flies,  bees,  etc.,  reduced  to  a  pulp 
by  mastication;  occasionally  wasps  steal  honey  from  bees. 

The  workers,  as  is  usual  among  social  Hymenoptera,  are  modified 
females,  incapable  of  reproduction  as  a  rule,  though  the  distinction  be- 
tween worker  and  queen  is  not  nearly  so  sharp  among  wasps  as  it  is 
among  bees.  Worker  eggs  are  said  to  be  parthenogenetic  and  to  pro- 
duce only  males.  The  males,  unhke  those  of  the  honey  bee,  are  active 
laborers  in  the  colony.  In  the  tropics  there  are  wasps  that  form  per- 
manent colonies,  store  honey  and  swarm,  after  the  manner  of  honeybees. 

Polistes.— The  preceding  description  of  Vespa  applies  equally  well 
to  our  several  species  of  Polistes,  except  that  the  nest  of  Polistes  is  a 


INTERRELATIONS    OF   INSECTS  289 

single  comb  hanging  by  a  pedicel  and  without  a  protecting  envelope. 
Miss  Enteman,  who  has  carefully  studied  the  habits  of  Polistes,  finds 
that  the  larva  spins  a  lining  as  well  as  a  cap  for  its  cell,  by  means  of  a 
fluid  from  the  mouth,  and  that  the  adults  emerge  after  a  pupal  period  of 
three  weeks,  males  and  females  appearing  (in  the  vicinity  of  Chicago) 
in  the  latter  part  of  August  and  early  in  September.' 

Ants 

The  habits  of  ants  have  engaged  the  serious  attention  of  some  of  the 
most  sagacious  students  of  the  phenomena  of  life.  Any  species  of  ant 
presents  innumerable  problems  to  the  thoughtful  investigator  and  about 
five  thousand  species,  subspecies  and  varieties  of  ants  have  been 
described. 

A  large  part  of  our  knowledge  of  the  habits  of  these  remarkable 
insects  has  been  obtained  by  the  use  of  artificial  formicaries,  which  are 
easily  constructed  and  have  yielded  important  results  in  the  hands  of 
Lubbock,  Forel,  Janet,  Wasmann,  Fielde,  Wheeler  and  other  well- 
known  students  of  ants.  We  have  an  important  comprehensive  volume 
on  these  insects  by  Wheeler. 

Castes. — In  a  colony  of  ants  three  kinds  of  individuals  are  produced 
as  a  rule:  males,  females  and  workers,  the  last  being  sexually  imperfect 
females. 

The  males  and  females  swarm  into  the  air  for  a  nuptial  flight,  after 
which  the  males  die,  but  the  females  shed  their  wings  and  enter  upon  a 
new  and  prolific  existence,  which  may  last  for  many  years;  a  queen  of 
Lasius  niger  was  kept  alive  by  Lubbock  for  nine  years,  and  one  oi Formica 
fusca,  fifteen  years,  and  then  its  death  was  due  to  an  accident. 

The  workers  live  from  one  to  seven  years,  according  to  the  same 
authority.  They  constitute  the  vast  majority  in  any  colony  and  are  the 
familar  forms  that  so  often  command  attention  by  their  industry  and 
pertinacity.  In  some  species  certain  of  the  workers  are  known  as 
soldiers;  these  may  be  recognized  by  their  larger  head  and  mandibles. 

Pol3miorphism. — Ants  and  termites  surpass  all  other  insects  in 
respect  to  the  number  of  forms  under  which  a  single  species  may  occur. 
In  some  species  of  ants  several  types  of  workers  exist;  these  are  distin- 
guished by  structural  peculiarities  of  one  kind  or  another,  which 
possibly  indicate  special  functions,  for  the  most  part  as  yet  unas- 
certained. Furthermore,  the  sexual  individuals  are  not  necessarily 
winged;  some  or  all  of  them  may  be  wingless,  especially  the  females. 


290  ENTOMOLOGY 

These  wingless  males  and  females  are  termed  ergatoid,  on  account  of 
their  resemblance  to  workers. 

As  to  how  these  various  forms  are  produced,  very  little  is  known. 
Probably,  as  among  bees,  workers  and  queens  are  produced  from  the 
same  kind  of  eggs,  which  have  been  fertilized,  and  the  differences 
between  worker  and  queen  and  between  workers  themselves  may  be  due 
to  the  quality  and  quantity  of  the  food  that  is  supplied  to  the  larvae 
by  their  nurses.  As  in  bees,  the  parthenogenetic  eggs  laid  by  abnormal 
workers  may  produce  males,  as  Forel,  Lubbock  and  Miss  Fielde  have 
found;  or  they  may  produce  normal  workers,  as  Reichenbach  and  Mrs. 
A.  B.  Comstock  have  found  to  be  the  case  in  Lasius  niger.  Wheeler 
points  out  the  possibility  of  the  inheritance  of  worker  characters  through 
the  male  offspring  of  workers. 

Larvae. — The  numerous  eggs  laid  by  one  or  more  queens  are  taken 
in  charge  by  the  young  workers,  through  whose  assiduous  care  the  help- 
less larvae  are  carried  to  maturity.  The  nurses  feed  the  larvae  from  their 
own  mouths,  clean  the  larvae,  and  carry  them  from  one  place  to  another 
in  order  to  secure  the  optimum  conditions  of  temperature,  moisture,  etc. 
When  a  nest  is  broken  open,  the  workers  seize  the  larvae  and  pupae  and 
hurry  into  some  dark  place.  The  pupa  is  either  naked  or  else  enclosed 
in  a  cocoon,  spun  by  the  larva. 

Nests. — The  species  of  the  tropical  genus  Eciton  do  not  make  nests 
but  occupy  temporarily  any  suitable  retreat  which  they  may  happen  to 
find  in  the  course  of  their  wanderings.  Ants  in  general  know  how  to 
utilize  all  sorts  of  existing  cavities  as  nests;  they  make  use  of  crevices 
in  rocks  and  under  stones  or  bark,  the  holes  made  by  bark-beetles,  hollow 
stems  or  roots,  plant-galls,  fruits,  etc.  The  extraordinary  "ant-plants" 
have  already  received  special  consideration. 

Very  many  ants  excavate  their  nests  in  the  ground ;  after  a  rain  these 
ants  are  especially  industrious  in  the  improvement  of  the  nest,  pressing 
the  wet  earth  into  the  walls  of  the  galleries  and  adding  probably  a  se- 
creted fluid  which  acts  as  a  cement;  stones  and  sticks  are  often  worked 
into  the  walls  of  a  nest  and  the  mounds  of  ants  are  frequently  fashioned 
about  blades  of  grass  or  growing  herbage  of  whatever  kind.  The  sub- 
terranean galleries  are  often  complex  labyrinths;  frequently  there  are 
long  underground  passages  extending  out  in  all  directions,  sometimes 
to  aphid-infested  roots  of  plants  or,  as  in  the  case  of  the  leaf-cutting 
ants  of  the  tropics,  to  trees  which  are  destined  to  be  attacked;  special 
chambers  are  set  apart  for  the  storage  of  food  and  others  for  eggs,  larvae 
or  pupae. 


INTERRELATIONS    OF    INSECTS  29I 

Often  a  nest  is  excavated  under  a  stone.  As  Forel  observes,  the 
stone  warms  speedily  under  the  rays  of  the  sun,  and  in  damp  or  cool 
weather  the  ants  are  always  in  the  highest  story  of  the  nest  as  soon  as 
the  sun's  warmth  begins  to  penetrate  the  soil,  while  they  go  below  as 
soon  as  the  sun  disappears  or  when  its  heat  becomes  too  strong.  They 
select  stones  that  are  neither  too  large  nor  too  small  to  regulate  the  tem- 
perature well,  while  other  ants  attain  the  same  object  by  making  the 
nest  under  sheltering  herbage  or  by  making  a  mound  with  a  hard 
cemented  roof. 

The  well-known  ant-hills  may  consist  simply  of  excavated  particles 
of  soil  or  else,  as  in  the  huge  mounds  of  Formica  exsectoides,mz,ycontdi\n 
labyrinthine  passages  in  addition  to  those  underground.  The  mounds 
of  this  species  are  elaborate  structures  which  may  last  a  man's  lifetime 
at  least.  F.  exsectoides  is  accustomed  to  form  new  colonies  in  connec- 
tion with  the  parent  nest;  McCook  found  in  the  Alleghanies  no  less  than 
1,600  nests,  forming  a  single  enormous  community  with  hundreds  of 
millions  of  inhabitants,  hostile  to  all  other  colonies  of  ants,  even  those 
of  the  same  species.  This  ant  covers  its  mound  with  twigs,  dead  leaves, 
grass  and  all  sorts  of  foreign  material,  and  is  said  to  close  the  exits  of  the 
nest  with  bits  of  wood  at  night  and  in  rainy  weather,  removing  them  in 
the  morning  or  when  the  weather  becomes  favorable. 

As  Forel  says  [translation]:  "The  chief  feature  of  ant  architecture, 
in  contradistinction  to  that  of  the  bees  and  the  wasps,  is  its  irregularity 
and  want  of  uniformity — that  is  to  say,  adaptability,  or  the  capacity  of 
making  all  the  surroundings  and  incidents  subserve  the  purpose  of  at- 
taining the  greatest  possible  economy  of  space  and  time  and  the  greatest 
possible  comfort.  For  instance,  the  same  species  will  live  in  the  Alps 
under  stones  which  absorb  the  rays  of  the  sun;  in  a  forest  it  will  live  in. 
warm,  decayed  trunks  of  trees;  in  a  rich  meadow  it  will  live  in  high, 
conical  mounds  of  earth."  Some  species  construct  peculiar  pasteboard 
nests,  as  Lasius  fuliginosus  of  Europe  and  tropical  species  of  Cremasto- 
gaster;  and  others  spin  silk  to  fasten  leaves  together,  as  Polyrhachis  of 
India  and  (Ecophylla  of  tropical  Asia  and  tropical  Africa,  the  silk  being 
probably  a  salivary  secretion,  according  to  Forel. 

Habits  in  General. — The  habits  of  ants  are  an  inexhaustible  and 
ever-fascinating  subject  of  study  to  the  naturalist,  and  well  repay  the 
most  critical  observation.  While  each  species  has  its  characteristic 
habits,  ants  in  general  have  many  customs  in  common. 

Thus  ants  of  one  colony  exhibit,  as  a  rule,  a  pronounced  hostiHty. 
toward  ants  of  any  other  colony,  even  one  of  the  same  species,  but 


292  ENTOMOLOGY 

recognize  and  spare  members  of  their  own  colony,  even  after  many 
months  of  separation  and  though  the  colony  may  number  half  a  million 
individuals.  This  recognition  is  effected  by  means  of  an  odor,  dis- 
tinctive of  the  colony  and  apparently  inheritable.  When  an  ant  is 
washed  and  then  restored  to  its  fellows,  it  is  treated  at  first  as  an  intru- 
der and  may  even  be  killed.  The  same  is  true  when  the  ant  has  been 
smeared  with  juices  from  the  bodies  of  alien  ants.  According  to  Miss 
Fielde,  workers  of  colony  A,  smeared  with  the  juices  from  crushed  ants 
of  colony  B  and  then  placed  in  colony  B  are  received  amicably,  but  at 
once  set  about  to  destroy  their  hosts,  Uke  "wolves  in  sheep's  clothing." 
These  statements  apply  only  to  workers,  however,  for  alien  larvae  and 
pupae  are  frequently  captured  and  reared  by  ants,  and  Miss  Fielde 
states  that  kings  of  one  colony  of  Stenamma  when  introduced  into 
another  colony  are  even  cordially  received. 

Some  of  the  most  careful  students  of  the  habits  of  ants  agree  that 
these  insects  can  communicate  with  one  another.  An  ant  discovers  a 
supply  of  food,  returns  toward  the  nest,  meets  a  fellow  worker,  the  two 
stroke  antennae  and  then  both  start  back  to  the  food;  before  long  other 
members  of  the  colony  swarm  to  the  prize.  It  has  been  thought  that 
the  odor  of  the  food  or  some  other  odor,  left  by  the  first  ant,  serves  as  a 
trail  for  the  other  ants  to  follow.  Bethe,  indeed,  infers  from  his  ex- 
periments that  this  phenomenon  is  purely  mechanical  and  involves  no 
psychical  qualities  on  the  part  of  the  ants.  His  own  experiments,  how- 
ever, show  that  one  ant  can  inform  another  by  means  of  an  odor  as  to 
the  whereabouts  of  food — which  is  certainly  one  form  of  communication. 

Ants  avoid  sunlight  as  a  rule  but  prefer  rays  of  lower  refrangi- 
bility  to  those  of  higher.  Upon  exposing  ants  to  the  colors  of  the  spec- 
trum, as  transmitted  through  glasses  of  different  colors,  Lubbock  found 
that  they  congregated  in  greatest  numbers  under  the  red  glass  and  that 
the  numbers  diminished  regularly  from  the  red  to  the  violet  end  of  the 
spectrum,  there  being  very  few  individuals  under  the  violet  glass. 

Miss  Fielde,  experimenting  with  queens,  workers  and  young  of 
Stenamma  fulvum  piceum  in  an  artificial  nest,  covered  half  the  nest  with 
orange  glass  and  half  with  violet.  "The  ants  removed  hastily  from 
under  the  violet  as  often  as  an  interchange  of  the  panes  was  made,  once 
or  twice  a  day,  for  about  twenty  days.  Thereafter  they  became  indif- 
ferent to  the  violet  rays."  "The  plasticity  of  the  ants  is  remarkably 
shown  in  their  gradually  learning  to  stay  where  they  were  never  disturbed 
by  me,  under  rays  from  which  their  instincts  at  first  withdrew  them." 

Ants  are  sensitive  not  only  to  the  different  colors  of  the  spectrum 


INTERRELATIONS    OF    INSECTS  293 

but  also  to  the  ultra-violet  rays,  which  produce  no  appreciable  effect 
on  the  human  retina  (though  they  induce  chemical  changes) .  If  obliged 
to  choose  between  the  two,  ants  prefer  violet  to  ultra-violet  rays,  as 
Lubbock  found.  If,  however,  the  ultra-violet  rays  are  intercepted,  by 
means  of  a  screen  of  sulphate  of  quinine  or  bisulphide  of  carbon,  the  ants 
then  collect  under  the  screen  in  preference  to  under  the  violet  rays. 

From  lack  of  experience  we  can  form  no  adequate  idea  as  to  the  range 
of  sensation  in  ants  or  other  insects.  Ants  can  taste  substances  that  we 
cannot,  and  vice  versa.  They  show  no  response  to  sounds  of  human 
contrivance,  yet  many  of  them  possess  stridulating  organs  and  organs 
that  are  doubtless  auditory;  whence  it  may  be  inferred  that  ants  can 
communicate  with  one  another  by  means  of  sounds.  In  rare  instances 
the  stridulation  of  an  ant  can  impress  the  human  ear,  as  in  a  species  of 
Atta  mentioned  by  Sharp. 

Experiments  show  that  ants,  as  well  as  bees  and  wasps,  find  their 
way  back  to  the  nest,  not  by  a  mysterious  "sense  of  direction,"  but  by 
remembering  the  details  of  the  surroundings,  and  in  the  case  of  ants,  by 
means  of  an  odor  left  along  the  trail. 

In  studying  the  habits  of  ants,  the  greatest  care  must  be  exercised  in 
order  to  discriminate  between  actions  that  may  be  regarded  as  purely 
instinctive  and  those  that  may  indicate  some  degree  of  intelligence.  If 
any  insects  show  signs  of  intelligence,  the  social  Hymenoptera  do;  but 
in  the  study  of  this  recondite  subject,  false  conclusions  can  be  avoided 
only  by  observation  and  experimentation  of  the  most  critical  kind. 

Hunting  Ants.^ — Some  ants,  as  Formica  fusca,  live  by  the  chase, 
hunting  their  prey  singly.  The  African  "driver  ants "  {Anomma  arcens) , 
although  bhnd,  hunt  in  immense  droves,  consuming  all  the  animal  refuse 
in  their  way,  devouring  all  the  insects  they  meet,  and  not  hesitating  to 
attack  all  kinds  of  vertebrates;  these  ants  ransack  houses  from  time  to 
time  and  clear  them  of  all  vermin,  though  they  themselves  are  a  great 
nuisance  to  the  householder.  The  Brazilian  species  of  Eciton  (Fig.  290, 
jB,  C)  have  similar  habits  and  are  likewise  blind,  or  else  have  but  a  single 
lens  on  each  side  of  the. head.  These  insects  hunt  in  armies  of  hundreds 
of  thousands,  to  the  terror  of  every  animate  thing  they  come  across* 
They  have  no  permanent  abode,  but  now  and  then  appropriate  some 
convenient  hole  for  the  purpose  of  raising  a  new  brood  of  marauders. 

Slave-making  Ants.— It  is  a  fact  that  some  ants  make  slaves  of 
other  species.  Formica  sanguinea,  for  example,  will  attack  a  colony  of 
Formica  fusca,  kill  its  active  members  in  spite  of  their  determined  re- 
sistance, kidnap  the  larvae  and  pupae  and  carry  them  home,  where  the 


294 


ENTOMOLOGY 


captives  receive  every  care,  and  at  length,  as  imagines,  serve  their  mas- 
ters as  faithfully  as  they  would  serve  their  own  species.  In  the  Alle- 
ghanies,  according  to  McCook,  colonies  of  F.fusca  occur  where  there  are 
no  "red  ants"  {F.  sanguinea) ,  but  are  hard  to  find  where  the  enslaving 
species  occurs. 

Although  F.  sanguinea  can  exist  very  well  without  slaves,  Polyergus 
rufescens,  of  Europe,  is  notoriously  dependent  upon  their  services,  it 
being  doubtful  whether  it  is  capable  of  feeding  itself.  This  species  is 
powerful  as  a  warrior,  but  its  mandibles  are  of  little  use,  except  to  pierce 
the  head  of  an  adversary.  Strongylonotus  is  still  more  helpless,  while 
Aner gates  (also  of  Europe)  is  said  to  depend  absolutely  upon  its  slaves. 

Polyergus  lucidus  occurs  in  the  AUeghanies,  where  the  colonies  of  this 
species,  according  to  McCook,  contain  large  numbers  of  the  workers  of 
Formica  schaufussi.  The  masters  are  good  fighters  but  do  no  other 
work,  and  have  not  been  seen  to  feed  themselves,  though  they  may  often 
be  seen  feeding  from  the  mouths  of  their  slaves. 

Honey  Ants.— Among  ants  in  general,  the  workers  that  stay  in  the 


Pig.  289.- 


-Honey  ants,  Myrmecocyslus  melliger,  clinging  to  the  roof  of  their  chamber. 
About  natural  size. — After  McCook. 


nest  receive  food  from  the  mouths  of  the  foragers — a  custom  which  has 
led  to  the  extraordinary  conditions  found  in  the  "honey  ants,"  in  which 
certain  of  the  workers  sacrifice  their  own  activity  in  order  to  act  as  liviilg 
reservoirs  of  food  (repletes)  for  the  benefit  of  the  other  members  of  the 
colony.  This  remarkable  habit  has  arisen  independently,  in  different 
genera  of  ants,  in  North  America,  Australia  and  South  Africa,  as  Lub- 
bock observes. 


INTERRELATIONS    OF    INSECTS  295 

The  honey  ant  whose  habits  are  best  known,  through  the  studies  of 
McCook  and  others,  is  Myrmecocystus  melliger,  of  Mexico,  New  Mexico 
and  southern  Colorado.  In  this  species  some  of  the  workers  hang  slug- 
gishly from  the  roof  of  their  little  dome-like  chamber,  several  inches 
underground,  and  act  as  permanent  receptacles  for  the  so-called  honey, 
which  is  a  transparent  sugary  exudation  from  certain  oak-galls;  it  is 
gathered  at  night  by  the  foraging  workers  and  regurgitated  to  the 
mouths  of  the  "honey-bearers,"  whose  crops  at  length  become  dis- 
tended with  honey  to  such  an  extent  that  the  insects  (Fig.  289)  look 
like  so  many  little  translucent  grapes  or  good-sized  currants.  This 
stored  food  is  in  all  probability  drawn  upon  by  the  other  ants  when 
necessary. 

Leaf-cutting  Ants. — The  most  dangerous  foes  to  vegetation  in 
tropical  America  are  the  several  species  of  AUa  (Fig.  290,  A).    Living 


Fig.   290. — A,  leaf -cutting  ant,  Alia  cephaloies.     B,  wandering  ant,  Eciton  drepanophorum; 
C,  Eciton  omnivorum.     Natural  size. — After  Shipley. 

in  enormous  colonies  and  capable  of  stripping  a  tree  of  its  leaves 
in  a  few  hours,  these  formidable  ants  are  the  despair  of  the  planter; 
where  they  are  abundant  it  becomes  impossible  to  grow  the  orange, 
coffee,  mango  and  many  other  plants.  These  ants  dig  an  extensive 
underground  nest,  piling  the  excavated  earth  into  a  mound,  sometimes 
thirty  or  forty  feet  in  diameter,  and  making  paths  in  various  directions 
from  the  nest  for  access  to  the  plants  of  the  vicinity;  Belt  often  found 
these  ants  at  work  half  a  mile  from  their  nest;  they  attack  flowers, 
fruits  and  seeds,  but  chiefly  leaves.  Each  ant,  by  laboring  four  or  five 
minutes,  bites  out  a  more  or  less  circular  fragment  of  a  leaf  (Fig.  291) 
and  carries  it  home,  or  else  drops  it  for  another  worker  to  carry;  and 
two  strings  of  ants  may  be  seen,  one  carrying  their  leafy  burdens  toward 
the  nest,  the  other  returning  for  more  plunder. 

The  use  made  of  these  leaves  has  been  the  subject  of  much  discus- 
sion. Belt  found  the  true  explanation,  but  it  remained  for  Moller  to 
investigate  the  subject  so  thoroughly  as  to  leave  no  room  for  doubt. 
The  ants  grow  a  fungus  upon  these  leaves  and  use  it  as  food.  The  bits 
of  leaves  are  kneaded  into  a  pulpy,  spongy  mass,  upon  which  the 


296 


ENTOMOLOGY 


fungus  at  length  appears.  The  food  for  the  sake  of  which  the  ants 
carry  on  their  complex  operations  consists  of  the  knobbed  ends  of 
fungus  threads  (Fig.  292),  and  these  bodies,  rich  in  fluid,  form  the  most 
important,  if  not  the  sole  food  of  the  leaf-cutting  ants.  By  assiduously 
weeding  out  all  foreign  organisms  the  ants  obtain  a  pure  culture  of  the 

fungus,  and  by  pruning  the  fungus 
they  keep  it  in  the  vegetative  con- 
dition and  prevent  its  fructification; 
under  exceptional  circumstances, 
nevertheless,  the  fungus  develops 
aerial  organs  of  fructification  of  the 


Fig.  291. — A,  B,  cuts  made  Fig.     292. — Fungus     clumps     {Roziles 

in  Cuphea  leaves  in  four  or  five  gongylophora)  cultivated  by    ants    of   the 

minutes    by    Atta     discigera;  genus    A  Ha.     Greatly    magnified. — After 

natural    size.     C,     Atta     dis-  Moller. 

cigera  transporting  severed 
fragments  of  leaves;  reduced. — 
After  Moller. 

agaricine  type,  but  this  species  (Rozites  gongylophora)  has  never  been 
found  outside  of  ants'  nests.  The  pecuHar  clubbed  threads  were 
produced  by  Moller  in  artificial  cultures  and  are  not  spores,  but  prod- 
ucts of  cultivation.  Other  ants  are  known  to  cultivate  other  kinds 
of  fungi  for  similar  purposes. 

McCook  has  found  a  leaf-cutting  ant  {Atta  fervens)  in  Texas,  and 
mentions  that  it  cuts  circular  pieces  out  of  leaves  of  chiefly  the  live-oak, 
these  being  dropped  to  the  ground  and  taken  to  the  nest  by  another 
set  of  workers.  He  records  an  underground  tunnel  of  Atta  fervens 
which  extended  448  feet  from  the  nest  and  then  opened  into  a  path  185 
feet  in  length;  the  tunnel  was  18  inches  below  the  surface  on  an  average, 
though  occasionally  as  deep  as  6  feet,  and  the  entire  route  led  with 
remarkable  precision  to  a  tree  which  was  being  defoHated. 


INTEREELATIONS    OF    INSECTS  297 

The  same  observer  has  given  also  a  brief  account  of  a  leaf-cutting  ant 
that  lives  in  New  Jersey.  This  species  {Trachymyrmex  septentrionalis) 
cuts  the  needle-like  leaves  of  seedling  pines  into  little  pieces,  which  are 
carried  to  the  nest.  Two  columns  of  workers  may  be  seen,  one  com- 
posed of  individuals  returning  to  the  nest,  each  with  a  piece  of  pine 
needle,  the  other  of  outgoing  workers.  The  nest  is  a  simple  structure, 
extending  some  seven  inches  underground  and  ending  in  a  chamber  in 
which  are  several  small  pulpy  balls,  consisting  probably  of  masticated 
leaves.  Further  studies  upon  our  own  leaf-cutting  ants,  modeled  after 
the  admirable  studies  of  Moller,  are  much  to  be  desired. 

Harvesting  Ants. — Lubbock  observes  that  some  ants  collect  the 
seeds  of  violets  and  grasses  and  preserve  them  carefully  for  some  purpose 
as  yet  unknown.  From  such  a  beginning  as  this  may  have  arisen  the 
extraordinary  habits  of  the  agricultural,  or  harvesting,  ants,  of  which 
some  twenty  species  are  known  from  various  parts  of  the  world. 

The  Texas  species  Pogonomyrmex  barbatus,  studied  by  Lincecum 
and  by  McCook,  clears  away  the  herbage  around  its  nest  (even  plants 
several  feet  high  and  as  thick  as  a  man's  thumb)  and  levels  the  ground, 
forming  a  disk  often  lo  or  12  and  sometimes  15  to  20  feet  in  diameter, 
from  which  radiating  paths  are  made,  from  60  to  300  feet  in  length. 
The  ants  go  back  and  forth  along  these  roads,  carrying  to  the  nest  seeds 
which  they  have  collected  from  the  ground  or  else  have  cut  from  plants ; 
these  seeds  are  stored  in  "granaries"  several  feet  underground  and  are 
eventually  used  as  food.  The  ants  prefer  the  seeds  of  a  grass,  Aristida 
oligantha,  but  the  oft-repeated  statement  that  they  sow  the  seeds  of  this 
"ant-rice,"  guard  it  and  weed  it,  is  denied  by  Wheeler. 

Notwithstanding  the  elaborate  studies  of  McCook  upon  this  subject, 
there  still  remain  not  a  few  essential  questions  to  be  answered. 

Myrmecophilism. — To  add  to  the  complexity  of  ant-life,  the  nests 
of  ants,  when  at  all  extensive,  are  frequented  by  a  great  variety  of  other 
arthropods,  which  on  account  of  their  association  with  ants  are  termed 
myrmecophiles.  Most  of* these  are  insects,  of  which  Wasmann  has 
catalogued  1,200  species,  but  not  a  few  are  spiders,  mites,  crustaceans, 
etc.  Though  the  diverse  relations  between  myrmecophiles  and  ants 
are  but  partially  understood,  these  aliens  may  for  convenience  be  con- 
sidered under  five  groM^?>:  captives^  guests,  visitors,  intruders  dind parasites. 

Captives. — Besides  enslaving  other  species,  as  already  mentioned, 
ants  make  use  of  aphids  and  some  coccids  for  the  sake  of  their  palatable 
products.  The  attendance  of  ants  upon  colonies  of  plant  lice  is  a  com- 
mon occurrence  and  one  that  repays  careful  observation.     With  the 


298  ENTOMOLOGY 

aid  of  a  hand-lens,  one  may  see  the  ants  hastening  about  among  the 
plant  lice  and  patting  them  nervously  with  the  antennae  until  at  length 
some  aphid  responds  by  emitting  from  the  end  of  the  abdomen  a  glisten- 
ing drop  of  watery  fluid,  which  the  ant  snatches.  This  fluid,  contrary 
to  prevalent  accounts,  is  not  furnished  by  the  so-called  honey-tubes  of 
the  aphid,  but  comes  from  the  alimentary  canal;  the  " honey- tubes "  are 
glandular  indeed,  but  are  probably  repellent  in  function.  In  some 
instances  ants  give  much  care  to  their  aphids,  for  example  covering  them 
with  sheds  of  mud,  which  are  reached  through  covered  passageways. 
More  than  this,  however,  some  ants  actually  collect  aphid  eggs  and  pre- 
serve them  over  winter  as  carefully  as  they  do  their  own  eggs.  In  one 
such  instance  Lubbock  found  that  the  aphids  upon  hatching,  after  six 
months,  were  brought  out  by  the  ants  and  placed  upon  young  shoots  of 
the  English  daisy,  their  proper  food  plant.  In  our  own  country,  as 
Forbes  has  discovered,  the  eggs  of  the  corn  root  louse  {Aphis  maidira- 
dicis)  are  collected  in  autumn  by  ants  (especially  of  the  genus  Lasius) 
and  stored  in  the  underground  nests.  In  winter  the  eggs  are  taken  to 
the  deepest  parts  of  the  nest,  and  on  bright  spring  days  they  are  brought 
up  and  even  scattered  about  temporarily  in  the  sunshine;  while  if  a  nest 
is  opened,  the  ants  carry  off  the  aphid  eggs  as  they  would  their  own. 
In  spring  the  ants  tunnel  to  the  roots  of  pigeon  grass  and  smar tweed, 
seize  the  aphids  and  carry  them  to  these  roots,  and  later  to  the  roots  of 
Indian  corn.  Throughout  the  year  the  ants  exercise  supervision  over 
these  aphids;  occasionally,  as  Forbes  says,  an  ant  seizes  a  winged  louse 
in  the  field  and  carries  it  down  out  of  sight,  and  in  one  such  instance  it 
appeared  that  the  wings  had  been  gnawed  away  near  the  body,  as  if  to 
prevent  the  escape  of  the  louse.  Similar  relations  exist  also  between 
ants  and  some  species  of  scale  insects. 

Guests. — Though  Aphididae  and  Coccidae  are  able  almost  always  to 
live  without  the  help  of  ants,  there  are  some  insects  which  have  never 
been  found  outside  the  nests  of  ants.  Most  of  these  insect  guests  are 
beetles,  notably  Staphylinidae  and  Pselaphidae.  The  rove-beetles  make 
themselves  useful  by  devouring  refuse  organic  matter,  and  these  scav- 
engers are  unmolested  by  the  ants  with  which  they  live.  A  few  myrme- 
cophilous  beetles  furnish  their  hosts  with  a  much-coveted  secretion  and 
receive  every  attention  from  the  ants,  which  clean  these  valuable  beetles 
and  even  feed  them  mouth  to  mouth,  as  the  ants  feed  one  another. 
Lomechusa  (Fig.  293)  is  one  of  these  favored  guests,  as  it  has  abdominal 
tufts  of  hairs  from  which  the  ants  secure  a  secreted  fluid.  Atemeles 
(Fig.  294)  is  another;  it  solicits  and  obtains  food  from  the  mouth  of  a 


INTERRELATIONS    OF   INSECTS 


299 


foraging  ant  as  if  it  were  an  ant  itself.  In  the  Alleghanies,  Atemeles 
cava  occurs  in  the  nests  of  Formica  rufa,  and  is  much  prized  by  this  ant 
on  account  of  the  fluid  which  the  beetle  secretes  from  glandular  hairs 
on  the  sides  of  the  abdomen. 

The  beetle  Claviger  has  at  the  base  of  each  elytron  a  tuft  of  hairs, 


Fig.  293. — Lomechusa  strumosa  being  freed  of  mites  by  Dinarda  dentata. — After  Wasmann. 


Fig.    294. — Atemeles    emarginatus   being    fed    by    an    ant,    Myrmica    scabrinodis. — After 

Wasmann. 


which  the  ants  lick  persistently.  This  beetle  is  blind  and  appears  to  be 
incapable  of  feeding  itself;  for  when  deprived  of  ant-assistance  it  dies, 
even  though  surrounded  by  food.  These  cases  of  symbiosis,  or  mutual 
benefit,  are  well  authenticated. 

Visitors.— Many  myrmecophilous  insects  are  not  restricted  to  ants' 
nests,  but  are  free  to  enter  or  to  leave.  This  is  true  of  such  Staphylinidae 
as  visit  formicaries  simply  for  shelter  or  to  feed  upon  detritus,  and  these 
visitors  are  treated  with  indifference  by  the  ants. 


300 


ENTOMOLOGY 


Intruders. — Not  so,  however,  with  species  that  are  inimical  to  the 
interests  of  the  ants,  such  as  many  species  of  StaphyUnidae  and  His- 
teridae,  which  steal  food  from  the  ants,  kill  them  or  devour  their  larvae 
or  pupae  at  every  opportunity.  The  ants  are  hostile  to  these  marauders, 
though  the  latter  often  escape  through  their  agihty  or  else  rely  upon 
their  armor  for  protection.  Quedius  brevis  and  Myrmedonia,  as  Schwarz 
observes,  are  soft-bodied  forms  which  remain  beside  the  walls  of  the  gal- 
leries or  near  the  entrance  of  a  nest  and  attack  solitary  ants;  while 
Hetcerius,  which  mixes  with  the  ants,  is  protected  by  its  hard  and  smooth 
covering,  under  which  the  legs  and  antennae  can  be  withdrawn.  Such 
an  enemy  is  an  unavoidable  evil  from  the  standpoint  of  an  ant. 


Fig.  295. — Atelura  formicaria  stealing  food  from  a  pair  of  ants. — After  Janet. 

Janet  has  described  the  amusing  way  in  which  an  audacious  species 
of  Atelura  steals  food  from  the  very  mouths  of  ants,  As  is  well  known, 
ants  are  accustomed  to  feed  one  another  from  mouth  to  mouth.  When 
the  foragers,  filled  with  honey  or  other  food,  return  to  the  nest,  they  are 
solicited  for  food  by  those  that  have  remained  at  home;  as  a  forager  and 
a  beggar  stand  head  to  head,  the  former  disgorges  small  drops  of  food, 
which  are  seized  by  the  latter.  While  a  pair  of  ants  are  engaged  in  this 
performance  (Fig.  295),  and  a  drop  of  honey  is  being  passed,  the  Atelura 
rushes  in,  grabs  the  drop  and  hurries  away.  As  might  be  expected, 
these  interlopers  are  constantly  being  chased  by  their  victims  from  one 
corner  of  the  nest  to  another. 

Parasites.^-Nematode  worms  occupy  the  pharyngeal  glands  of  ants; 
larvae  of  Stylops  inhabit  their  bodies;  more  than  thirty  kinds  of  mites 
attach  themselves  to  the  heads  or  feet  of  ants;  while  Chalcididae  and 
Proctotrypidae  parasitize  ants'  eggs. 


INTERRELATIONS    OF   INSECTS  3OI 

Origin  of  the  Social  Habit. — Wheeler  regards  "trophallaxis," 
meaning  exchange  of  nourishment,  as  the  source  of  the  social  habit  in 
wasps,  ants,  and  termites;  though  admitting  that  the  phenomenon  has 
not  been  observed  in  the  social  bees.  He  says:  "If  we  confine  our 
attention  largely  to  the  ants,  I  believe  it  can  be  shown  that  trophallaxis, 
originally  developed  as  a  mutual  trophic  relation  between  the  mother 
insect  and  her  larval  brood,  has  expanded  with  the  growth  of  the 
colony  like  an  ever-widening  vortex  till  it  involves,  first,  all  the  adults 
as  well  as  the  brood  and  therefore  the  entire  colony;  second,  a  great 
number  of  species  of  ahen  insects  that  have  managed  to  get  a  foothold 
in  the  nest  as  scavengers,  praedators  or  parasites  (symphily);  third, 
alien  social  insects — i.e.,  other  species  of  ants  (social  parasitism); 
fourth,  alien  insects  that  live  outside  the  nest  and  are  ''milked"  by 
the  ants  (trophobiosis) ;  and,  fifth,  certain  plants  which  are  visited  or 
sometimes  partly  inhabited  by  the  ants  (phytophily)." 


CHAPTER  XI 

INSECT  BEHAVIOR 

The  subject  of  insect  behavior  will  be  considered  under  three  heads ; 
(i)  Tropisms,  (2)  Instinct,  (3)  IntelHgence. 

I.  Tropisms 

Environmental  influences,  such  as  light,  temperature  or  moisture, 
may  control  the  direction  of  locomotion  of  an  organism  by  determining 
the  orientation  of  its  body.  The  reaction  of  the  organism  under  these 
circumstances  is  known  as  a  tropic,  or  tactic,  reaction.  A  moth,  for  ex- 
ample, flies  toward  a  flame — is  positively  phototropic;  a  cockroach,  on 
the  contrary,  avoids  the  Ught — is  negatively  phototropic.  A  plant  turns 
toward  the  sun — in  other  words,  is  positively  heliotropic. 

An  insect  flies  toward  the  Ught  as  inevitably  and  as  mechanically  as 
a  plant  turns  toward  the  sun;  indeed,  the  two  phenomena  are  funda- 
mentally the  same.  Some  students  prefer,  however,  to  use  the  term 
taxis  for  bodily  movements  of  motile  organisms,  and  the  term  tropism 
for  turning  movements  of  fixed  organisms. 

The  study  of  tropic  reactions  has  already  illuminated  the  entire 
subject  of  the  behavior  of  organisms  and  placed  it  on  a  rational  basis, 
and  the  complex  tropisms  of  insects  offer  a  fresh  and  large  field  to  the 
investigator. 

Chemotropism. — Positive  and  negative  chemotropism,  as  Wheeler 
observes,  "are  among  the  most  potent  factors  in  the  Uves  of  insects." 
Insects  are  affected  positively  or  negatively  by  such  substances  as  can 
affect  their  end-organs  of  smell  or  taste.  Positive  chemotropism 
enables  many  insects  to  find  their  food  or  their  mates;  and  negative 
chemotropism  enables  them  to  avoid  injurious  substances.  This 
negative  reaction  on  the  part  of  other  organisms  is  made  use  of  also  by 
such  insects  as  emit  repellent  odors. 

A  maggot  orients  its  body  with  reference  to  a  source  of  food  and  then 
moves  toward  the  food  just  as  mechanically  as  a  moth  flies  to  a  flame. 
The  maggot,  as  Loeb  maintains,  is  influenced  chemically  by  the  radiat- 
ing diffusion  from  a  piece  of  meat,  and  follows  a  line  of  diffusion  to  the 

302 


INSECT  BEHAVIOR  303 

center  of  diffusion  in  much  the  same  way  that  a  moth  follows  a  ray  of 
light  to  its  source.  In  both  cases  a  stimulus  affects  muscular  tissue; 
the  animal  orients  its  body  until  the  muscular  tension  is  symmetrically 
distributed,  and  then  locomotion  brings  the  animal  to  the  source  of  the 
stimulus,  whether  it  be  food  or  light. 

The  remarkable  "instinctive"  action  of  the  fly  in  laying  her  eggs  on 
meat  is  due,  according  to  Loeb,  simply  to  the  fact  that  both  the  fly  and 
the  maggot  have  the  same  kind  of  positive  chemotropism.  Similarly 
also  in  the  case  of  such  butterflies  or  other  insects  as  lay  their  eggs  on  a 
special  kind  of  plant.  It  is  certain  that  "neither  experience  nor  voHtion 
plays  any  part  in  these  processes." 

W.  M.  Barrows  determined  experimentally  that  the  well-known 
pomace  fly,  Drosophila  ampelophila,  is  positively  chemotropic  to  amyl 
alcohol,  ethyl  alcohol,  acetic  acid,  lactic  acid  and  other  chemical  sub- 
stances, all  of  which  occur  in  fermenting  fruits.  The  fly  finds  its  food, 
not  by  sight,  but  by  smell,  and  when  this  sense  is  lost  it  reaches  its  food 
only  by  accident.  The  olfactory  sense  organs  that  are  concerned  with 
finding  food  are  located  in  the  third  or  terminal  segment  of  the  antenna. 
When  one  antenna  is  lost  and  the  other  antenna  is  stimulated  by  food 
odor,  circus  movements  are  carried  out  in  such  a  way  as  to  prove  that 
the  fly  orients  normally  by  an  unequal  stimulation  of  the  antennae. 
Drosophila,  when  stimulated  by  a  weak  food  odor,  first  shows  random 
movements,  i.e.,  it  attempts  to  find  the  food  by  the  method  of  trial  and 
error,  but  as  the  fly  passes  into  an  area  of  greater  stimulation,  these 
movements  give  way  to  a  direct  orientation. 

Hydrotropism. — Wheeler  observed  that  beetles  of  the  genera  Hali- 
plus  and  Hydroporus  were  positively  hydrotropic;  that  when  released  on 
the  shore  from  a  bunch  of  water  plants,  they  scrambled  toward  the  lake, 
twenty  feet  away.  Collectors  take  advantage  of  the  negative  hydro- 
tropism of  Bembidion,  Elaphrus,  Omophron  and  other  shore-dwelling 
beetles  by  splashing  the  water  upon  the  dry  bank,  when  the  beetles  leave 
their  places  of  concealment  and  are  easily  caught. 

It  is  well  known  that  after  a  rain  ants  carry  their  young  out  into  the 
sunshine,  though  when  the  upper  parts  of  the  nest  become  too  dry,  the 
ants  transfer  their  eggs,  larvae  and  pupae  to  lower  and  moister  galleries. 
In  these  instances,  however,  we  have  to  deal  with  thermotropism  as  well 
as  hydrotropism. 

Thigmotropism. — Negative  thigmotropism  (stereotropism)  as  dis- 
played in  the  withdrawal  from  contact,  is  a  common  phenomenon 
among  animals,  from  Protozoa  to  Vertebrata,  and  is  often  conducive 


304 


ENTOMOLOGY 


to  the  safety  of  an  organism;  though  the  negative  response  occurs 
none  the  less,  whether  it  is  to  prove  useful  or  not,  and  occurs  as  auto- 
matically as  the  collapse  of  a  sensitive  plant  at  a  touch. 

Positive  thigmotropism  is  less  common,  though  nevertheless  wide- 
spread among  animals.  Protozoa  and  Infusoria  cling  to  solid  bodies 
and  become  aggregated  about  them.  Cockroaches  squeeze  themselves 
into  crevices  until  their  bodies  come  into  close  contact  with  surrounding 
surfaces.  A  moth,  Pyrophila  (Amphipyra)  pyramidoides,  is  accustomed 
to  squeeze  into  crevices  under  loose  bark  or  elsewhere,  though  this  habit, 
though  doubtless  protective,  is  not  performed/or  the  purpose  of  self-con- 
cealment. That  this  is  not  a  case  of  negative  phototropism,  it  was 
proved  by  Loeb,  who  wrote -."Iplaced  some  of  these  animals  in  a  box,  one- 
half  of  which  was  covered  with  a  non- transparent  body,  the  other  half  with 
glass.  I  covered  the  bottom  of  the  box  with  small  glass  plates  which 
rested  on  small  blocks,  and  were  raised  just  enough  from  the  bottom  to 
allow  an  Amphipyra  to  get  under  them.  Then  the  Amphipyra  collected 
under  the  little  glass  plates,  where  their  bodies  were  in  contact  with 
solid  bodies  on  every  side,  not  in  the  dark  corner  where  they  would 
have  been  concealed  from  their  enemies.  They  even  did  this  when  in  so 
doing  they  were  exposed  to  direct  sunlight.  This  reaction  also  occurred 
when  the  whole  box  was  dark.  It  was  then  impossible  for  anything 
but  the  stereotropic  [thigmotropic]  stimuli  to  produce  the  reaction." 

Among  the  water-striders,  Gerridae,  thigmotropism  is  strongly  in 
evidence  at  the  inception  of  and  during  the  hibernation  period.  The 
gerrids  hibernate  in  large  groups  or  clusters  under  dead  leaves,  in  holes 
in  banks  of  streams,  under  logs,  etc.,  with  their  bodies  in  close  contact 
with  the  substratum.  The  acts  of  crawling  into  and  remaining  in  such 
places  are  evidently  due  to  the  contact  stimuH  that  impinge  on  them  at 
such  times  (C.  F.  C.  Riley). 

Rheotropism. — Fishes  swimming  or  heading  directly  against  a  cur- 
rent of  water  illustrate  positive  rheotropism.  When  facing  the  current, 
the  resistance  of  the  water  is  symmetrically  distributed  on  the  body  of 
the  animal  and  is  met  by  symmetrical  muscular  action,  in  the  most  eco- 
nomical manner.  Many  aquatic  insects  offer  such  examples  of  rheo- 
tropism, either  positive  or  negative. 

E.  P.  Lyon  gives,  however,  a  different  explanation.  He  found  that 
fishes  orient  themselves  just  as  well  when  they  are  put  into  a  closed 
glass  bottle,  which  is  dragged  through  the  water,  although  in  this  case 
they  are  not  under  the  influence  of  any  friction  from  the  current.  When 
the  bottle  is  not  moved  the  fishes  swim  in  any  direction  inside  the 


INSECT   BEHAVIOR  305 

bottle.  It  is  obviously  the  motion  of  the  retina  images  of  the  objects 
on  the  bank  of  the  brook  which  causes  the  "rheotropic"  orientation  of 
fishes.  When  driven  backward  by  the  current  or  when  dragged  back- 
ward in  a  bottle  through  the  water,  the  objects  on  the  bank  of  the  river 
seem  to  move  in  the  opposite  direction.  The  animal  being  compelled 
to  keep  the  same  object  fixed,  an  apparent  forward  motion  of  the  fixed 
object  changes  the  muscles  of  the  fins  in  such  a  sense  as  to  cause  the 
animal  to  follow  the  fixed  object  automatically.  When  such  rheotropic 
fishes  were  kept  in  an  aquarium  and  a  white  sheet  of  paper  with  black 
stripes  was  moved  constantly  in  front  of  the  aquarium  the  fishes  ori- 
ented themselves  against  the  direction  in  which  the  paper  and  its 
stripes  moved.  The  phenomenon  was  more  marked  in  young  than  in 
older  specimens.  All  the  phenomena  of  rheotropism  ceased  in  the  dark 
or  when  the  fishes  were  blind.     (J.  Loeb.) 

Anemotropism. — Various  flies  orient  the  body  with  reference  to  the 
direction  of  the  wind.  Wheeler  observed  swarms  of  the  male  of  Bibio 
alhipennis  poising  in  the  air,  with  all  the  flies  headed  directly  toward  the 
gentle  wind  that  was  blowing.  If  the  wind  shifted,  the  insects  at  once 
changed  their  position  so  as  again  to  face  to  windward;  a  strong  wind, 
however,  blew  them  to  the  ground.  The  males  of  an  anthomyiid 
{Ophyra  leucostoma),  according  to  the  same  naturalist,  hover  in  swarms 
in  the  shade  for  hours  at  a  time;  if  the  breeze  subsides  they  lose  their 
definite  orientation,  but  if  it  is  renewed  they  face  the  wind  with  mihtary 
precision.  In  Syrphidae,  he  finds,  either  males  or  females  are  positively 
anemotropic.  Midges  of  the  genus  Chironomus,  which  on  summer  days 
dance  in  swarms  for  hours  over  the  same  spot,  orient  themselves  to 
every  passing  breeze.  So  also  in  the  case  of  Empididas,  which  Wheeler 
has  observed  swarming  in  one  spot  every  day  for  no  less  than  two  weeks, 
possibly  on  account  of  "some  odor  emanating  from  the  soil  and  attract- 
ing and  arresting  the  flies  as  they  emerged  from  their  pupas." 

The  Rocky  Mountain  locusts  "move  with  the  wind  and  when  the 
air-current  is  feeble  are  headed  away  from  its  source;"  when  the  wind  is 
strong,  however,  they  turn  their  heads  toward  it. 

Anemotropism  and  rheotropism  are  closely  allied  phenomena.  As 
Wheeler  says,  "The  poising  fly  orients  itself  to  the  wind  in  the  same  way 
as  the  swimming  fish  heads  upstream,"  adjusting  itself  to  a  gaseous 
instead  of  a  liquid  current.  "In  both  cases  the  organism  naturally 
assumes  the  position  in  which  the  pressure  exerted  on  its  surface  is  sym- 
metrically distributed  and  can  be  overcome  by  a  perfectly  symmetrical 
action  of  the  musculature  of  the  right  and  left  halves  of  the  body." 


3o6 


ENTOMOLOGY 


Geotropism.- — Gravity  frequently  determines  the  orientation  and 
direction  of  locomotion  of  an  animal.  A  freshly  emerged  moth  hangs 
with  the  abdomen  downward  and  remains  in  this  position  until  the 
wings  have  expanded.  Certain  dolichopodid  flies  found  on  the  bark 
of  trees  "rest  or  walk  with  the  long  axis  of  the  body  perpendicular  to 
the  earth  and  parallel  with  the  long  axis  of  the  trunk  of  the  tree  and  the 
head  pointing  upwards.  •  When  disturbed  they  fly  off,  but  very  soon 
alight  nearer  the  earth  and  again  walk  upward."  (Wheeler.)  Cocci- 
nellidas  (lady  beetles)  and  cockroaches  are  also  negatively  geotropic. 

The  latter  insects,  as  Loeb 
has  observed,  tend  to  leave 
a  horizontal  surface  but 
come  to  rest  on  a  surface 
that  is  vertical  or  as  nearly 
so  as  possible. 

Wheeler  says, "  Geotro- 
pic as  well  as  anemotropic 
orientation  is  not  altered 
for  the  sake  of  response  to 
light.  Even  if  the  insect 
be  strongly  heliotropic,  as 
is  the  case  inmost  Diptera, 
it  orients  itself  to  the  wind 
or  to  gravity  no  matter 
whence  the  light  may  fall." 
Experiments  by  W.  H. 

Fig.  296. — yl ,  tracks  made  on  paper  by  a  larva  of  Cole  shoW  that  the  pomace 

Lucilia  casar  moving  out  of  a  spot  of  ink  under  the  n  t-w  .7-7  .7 

influence  of  light;  a  and  B  show  respectively  the  first  AY'     i^rOSOpHlla     ampelO- 

and  second  directions  of  the  light.     jB,  tracks  made  in  -hfiHa       when      creeoinff 

the  dark.— After  Pouchet.  r  j  ^  F        a> 

reacts  negatively  to  grav- 
ity, to  a  centrifugal  force  which  is  equal  to  or  sUghtly  greater  than 
gravity,  and  to  air  currents  without  regard  to  other  stimuli.  Gravity 
is,  then,  a  kinetic  as  well  as  a  directive  stimulus.  The  stimuli  caus- 
ing these  reactions  are  probably  received  by  the  sensory  nerves  of  the 
leg  muscles.     (Cole.) . 

Phototropism.— It  is  a  matter  of  common  observation  that  house 
flies,  butterflies,  bees  and  many  other  diurnal  insects  fly  toward  the 
light;  and  that  cockroaches  and  bedbugs  avoid  the  light.  These  are 
familiar  examples  of  phototropism  {heliotropism)  or  the  ''control  of  the 
direction    of    locomotion    by    light."     The    phototropic    response    is 


INSECT  BEHAVIOR  307 

either  positive  or  negative  according  as  the  organism  moves,  respec- 
tively, toward  or  away  from  the  source  of  light.  Maggots  of  Lucilia 
ccesar  and  of  many  other  flies  are  negatively  phototropic  as  a  rule  (Fig. 
296,  A),  but  in  the  absence  of  light  (other  directive  stimuH  being 
excluded,  of  course)  wander  about  indifferently  (Fig.  296,  B). 

Do  the  different  rays  of  the  spectrum  differ  in  phototropic  power? 
This  question  has  occurred  to  many  investigators,  who  have  found  that, 
in  general,  the  rays  of  shorter  wave  length,  as  violet  or  blue,  are  more 
effective  than  those  of  longer  wave  length,  as  yellow  or  red;  the  latter  in 
fact  acting  like  darkness.  Ants  avoid  violet  rays  as  they  would  avoid 
direct  sunlight,  but  carry  on  their  operations  under  yellowish  red  Hght 
as  they  would  in  darkness.  Miss  Fielde  has  made  use  of  this  fact  in 
studying  the  habits  of  ants,  by  using  as  a  cover  for  her  artificial  formi- 
caries an  orange-red  sheet  of  glass  such  as  the  photographer  uses  for  his 
dark  room.  Though  ants  avoid  violet  rays,  they  prefer  them  to  ultra- 
violet rays,  as  Lubbock  found. 

These  responses  to  light  are  inevitable  on  the  part  of  the  organism, 
whether  they  are  beneficial  or  harmful,  and  it  is  now  becoming  recog- 
nized that  the  reactions  of  both  plants  and  animals  to  light  are  funda- 
mentally the  same. 

Phototaxis  and  Photopathy. — A  phototropic  organism,  if  bilater- 
ally symmetrical,  orients  itself  with  the  head  directly  toward  or  else 
directly  away  from  the  source  of  light  and  moves  toward  or  away  from 
the  light,  as  the  case  may  be.  In  either  event  the  long  axis  of  the 
organism  becomes  parallel  with  the  rays  of  light.  Now  a  ray  of  light  is 
ever  diminishing  in  intensity  from  its  source,  and  it  would  seem  that 
differences  of  intensity  along  the  paths  of  light  rays  determine  the  orien- 
tation and  consequent  direction  of  locomotion  of  the  organism.  Some 
investigators,  however,  distinguish  between  the  effects  of  intensity  of 
light  and  those  of  its  direction.  Thus  by  ingeniously  contrived  experi- 
ments, it  has  been  found,  apparently,  that  Protista  (Strasburger), 
Daphnia  (Davenport  and  Cannon)  and  the  caterpillars  of  Porthesia 
(Loeb)  move  toward  a  source  of  light  even  while,  in  so  doing,  they  are 
passing  into  regions  of  less  intensity  of  illumination.  For  this  migration 
as  determined  by  the  direction  of  the  light  rays,  the  term  phototaxis  is  by 
some  authors  (as  Davenport)  reserved.  Usually,  however,  the 
direction  of  locomotion  does  depend  on  differences  of  intensity,  without 
regard  to  the  direction  whence  the  light  comes.  This  "migration 
towards  a  region  of  greater  or  less  intensity  of  light"  has  been  termed 
photopathy,  and  organisms  are  said  to  be  photophil  or  photophob,  accord- 


308  ENTOMOLOGY 

ing  as  they  move,  respectively,  toward  or  away  from  a  more  intensely 
illuminated  area. 

Verworn  and  others  maintain,  however,  that  differences  of  intensity 
are  sufficient  to  account  for  all  phototropic  phenomena. 

Optimum  Intensity. — It  has  been  found  that  there  is  a  certain 
optimum  degree  of  light,  differing  according  to  the  organism,  toward 
which  the  organism  will  move,  from  either  a  region  of  greater  illumina- 
tion or  one  of  less.  The  organism  appears  to  be  attuned  to  a  "certain 
range  of  intensity."  This  attunement  is  used  by  Davenport  to  explain 
apparent  anomalies  between  the  response  to  light  of  a  butterfly  and 
that  of  a  moth.  Butterflies  are  positively  phototropic  to  sunlight  and 
most  moths  are  negatively  so.  Why,  then,  do  moths  fly  toward  a  lamp 
or  an  electric  light?  The  answer  is  given  that  the  moth  is  positively 
phototropic  up  to  a  certain  intensity  of  light,  at  which  it  becomes  nega- 
tively phototropic.  "Butterflies  are  attuned  to  a  high  intensity  of 
light,. moths  to  a  low  intensity;  so  that  bright  sunlight,  which  calls 
forth  the  one,  causes  the  other  to  retreat.  On  the  other  hand,  a  light 
like  that  of  a  candle,  so  weak  as  not  to  stimulate  a  butterfly,  produces  a 
marked  response  in  the  moth."     (Davenport.) 

The  circhng  of  moths  and  other  insects  about  a  Hght  is  a  matter  of 
common  observation,  an  explanation  for  which  has  been  given  by  Loeb. 
Loeb  says,  "If  a  moth  be  struck  by  the  light  on  one  side,  those  muscles 
which  turn  the  head  toward  the  light  become  more  active  than  those  of 
the  opposite  side,  and  correspondingly  the  head  of  the  animal  is  turned 
toward  the  source  of  light.  As  soon  as  the  head  of  the  animal  has  this 
orientation  and  the  median-plane  (or  plane  of  symmetry)  comes  into  the 
direction  of  the  rays  of  light,  the  symmetrical  points  of  the  surface  of  the 
body  are  struck  by  the  rays  of  light  at  the  same  angle.  The  intensity 
of  light  is  the  same  on  both  sides,  and  there  is  no  reason  why  the  animal 
should  turn  to  the  right  or  left,  away  from  the  direction  of  the  rays  of 
light.  Thus  it  is  led  to  the  source  of  the  light.  Animals  that  move 
rapidly  (like  the  moth)  get  into  the  flame  before  the  heat  of  the  flame  has 
time  to  check  them  in  their  flight.  Animals  that  move  slowly  are 
affected  by  the  increasing  heat  as  they  approach  the  flame;  the  high 
temperature  checks  their  progressive  movement  and  they  walk  or  fly 
slowly  about  the  flame."  As  Loeb  insists,  the  moth  "does  not  fly  into 
the  flame  out  of  'curiosity,'  neither  is  it  'attracted'  by  the  light;  it  is 
only  oriented  by  it  and  in  such  a  manner  that  its  median-plane  is 
brought  into  the  direction  of  the  rays  and  its  head  directed  toward  the 


INSECT  BEHAVIOR  309 

source  of  light.  In  consequence  of  this  orientation  its  progressive 
movements  must  lead  it  to  the  source  of  light." 

Factors  Influencing  Phototropism. — The  response  of  an  organism 
to  light  is  influenced  by  previous  exposure  to  light,  by  temperature, 
moisture,  nutrition  and  other  factors,  all  of  which  have  to  be  taken  into 
account  in  experiments  on  phototropism. 

Loeb  found  that  larvae  of  the  brown-tail  moth,  Euproctis  chrysor- 
rhcea,  driven  by  the  warm  sunshine  out  of  the  nest  in  which  they  have 
hibernated,  crawl  upward  to  the  tips  of  branches  and  feed  upon  the 
buds  and  new  leaves.  This  self-preservative  "instinct"  is  purely  a 
response  to  light.  The  caterpillars  are  positively  phototropic,  and  as 
the  horizontal  components  of  the  surrounding  light  neutralize  each 
other,  only  the  light  from  above  is  effective  as  a  stimulus  to  orientation. 
After  feeding,  however,  the  larvae  are  no  longer  positively  phototropic 
and  crawl  downward;  in  other  words,  they  are  positively  phototropic 
only  so  long  as  they  are  unfed.  Here  the  kind  of  phototropism  is 
dependent  upon  nutrition. 

Phototropism  may  be  overruled  by  chemotropism  and  influenced  by 
conditions  of  metabolism,  as  Parker  found  for  the  butterfly  Vanessa 
antiopa.  In  his  words:  Vanessa  antiopa,  in  bright  sunlight,  comes  to 
rest  with  the  head  away  from  the  source  of  light,  that  is,  it  is  negatively 
phototropic,  when  the  surface  on  which  it  settles  is  not  perpendicular 
or  very  nearly  perpendicular  to  the  direction  of  the  sun's  rays.  When, 
however,  this  surface  is'perpendicular  to  the  sun's  rays  the  insect  settles 
without  reference  to  the  direction  of  the  rays.  When  feeding  or  near 
food  [such  as  running  sap]  the  butterflies  do  not  respond  phototropically. 

This  negative  phototropism  is  seen  only  in  intense  sunlight  and  after 
the  butterfly  has  been  on  the  wing,  i.e.,  after  a  certain  state  of  metab- 
olism has  been  established. 

V.  antiopa  creeps  and  flies  toward  a  source  of  light,  that  is,  it  is 
positively  phototropic  in  its  locomotor  responses.  Positive  photo- 
tropism also  occurs  in  intense  sunKght,  and  is  not  dependent  upon  any 
particular  phase  of  metabolism. 

Both  negative  and  positive  phototropism  in  this  species  are  inde- 
pendent of  the  "heat  rays"  of  sunlight. 

The  position  assumed  in  negative  phototropism  exposes  the  color 
patterns  of  the  wings  to  fullest  illumination,  and  probably  has  to  do 
with  bringing  the  sexes  together  during  the  breeding  season. 

To  these  may  be  added  other  important  conclusions  of  Parker's; 


3IO  ENTOMOLOGY 

No  light  reactions  are  obtained  from  the  butterfly  when  shadows  are 
thrown  upon  any  part  of  the  body  except  the  head.  When  one  eye  is 
painted  black  the  butterfly  creeps  or  flies  in  circles  ("circus  move- 
ments") with  the  unaffected  eye  always  toward  the  center.  When  both 
eyes  are  painted  black  all  phototropic  responses  cease  and  the  insect  fldes 
upward.  Butterflies  with  normal  eyes  liberated  in  a  perfectly  dark  room 
come  to  rest  near  the  ceiling.  _  This  upward  flight  in  both  cases  is  due 
to  negative  geotropism,  not  to  phototropic  activity. 

V.  antiopa  does  not  discriminate  between  lights  of  greater  or  less 
intensity  provided  they  are  all  of  at  least  moderate  intensity  and  of 
approximately  equal  size.  V.  antiopa  does  discriminate  between  light 
derived  from  a  large  luminous  area  and  that  from  a  small  one,  even  when 
the  hght  from  these  two  sources  is  of  equal  intensity  as  it  falls  on  the 
animal.  These  butterflies  usually  fly  toward  the  larger  areas  of  light. 
This  species  remains  in  flight  near  the  ground  because  it  reacts  positively 
to  large  patches  of  bright  sunlight  rather  than  to  small  ones,  even 
though  the  latter,  as  in  the  case  of  the  sun,  may  be  much  more 
intense. 

V.  antiopa  retreats  at  night  and  emerges  in  the  morning,  not 
so  much  because  of  light  differences,  as  because  of  temperature 
changes.  On  warm  days  it  will,  however,  become  quiet  or  active, 
without  retreating,  depending  upon  a  sudden  decrease  or  increase  of  light. 

The  maggots  of  the  muscid  Phormia  regina  are,  as  the  author  has 
observed,  negatively  phototropic  until  full  grown,  when  they  become 
positively  phototropic  for  an  hour  or  less,  leave  the  decaying  matter  in 
which  they  have  developed  and  wriggle  along  the  ground  toward  the 
sun;  or  if  the  sunhght  is  diffused  by  clouds,  wander  about  aimlessly, 
but  at  length  bury  themselves  in  the  ground  to  pupate.  Here  the 
positive  phototropism  just  before  pupation  is  adaptive. 

The  swarming  of  the  honey  bee  is  likewise  a  case  of  periodic  positive 
phototropism,  as  Kellogg  has  observed. 

Winged  ants  of  both  sexes  are  strongly  positively  phototropic  when 
they  swarm  from  the  ground  for  the  nuptial  flight.  After  mating, 
however,  the  female  becomes  negatively  phototropic  and  positively 
thigmo tropic;  enters  the  ground,  sheds  her  wings,  and  enters  upon  a 
subterranean  existence,  during  which  she  is  intensely  positively  thigmo- 
tropic.  In  connection  with  this  subject,  it  is  a  significant  fact  that  the 
pomace  fly,  Drosophila,  loses  its  phototropism  when  its  wings  are 
removed  artificially. 

In  autumn,  gravid  females  of  the  mosquito,  Culex  pipiens,  become 


INSECT  BEHAVIOR 


Strongly  negatively  phototropic  and  seek  dark  hibernation  quarters,  in 
spite  of  warm  temperatures  that  may  prevail.  If  hibernating  in  a 
warm  place  the  mosquito  becomes  positively  thigmotropic,  and  loses 
its  phototropism,  prolonged  exposure  to  strong  lights  producing  no 
response,  though  the  insect  responds  actively  to  mechanical  stimuli.  It 
is  also  negatively  geotropic,  as  it  always  assumes  a  position  with  the 
long  axis  of  the  body  perpendicular  to  the  earth  and  the  head  pointing 
upward.     (H.  B.  Weiss.) 

Though  adaptive  in  their  results,  these  phototropic  reactions  can 
scarcely  be  said  to  be  performed  on  account  of  their  usefulness.  They 
are  performed  anyway,  and  may  result  harmfully,  as  when  they  lead 
a  moth  into  a  flame  or,  to  take  a  more  natural  example,  when  they 
expose  an  insect  to  its  enemies. 

Phototropism  and  thermotropism,  either  together  or  singly,  as 
Wheeler  suggests,  may  explain  the  up  and  down  migration  of  insects  in 
vegetation.  "On  cold,  cloudy  days  few  insects  are  taken  because  they 
lurk  quietly  near  the  surface  of  the  soil  and  about  the  roots  of  the  vegeta- 
tion, but  with  an  increase  in  warmth  and  Hght  they  move  upwards 
along  the  stems  and  leaves  of  the  plants,  and,  if  the  day  be  warm  and 
sunny,  escape  into  the  air." 

F.  Payne  bred  sixty-nine  successive  generations  of  the  pomace  fly, 
Drosophila  ampelophila  in  the  dark  without  any  resultant  effect  upon 
either  the  eyes  or  the  phototropism  of  the  flies. 

Drosophila  is  usually  positively  phototropic,  but  R.  S.  McEwen 
obtained  a  mutant  which  is  not  phototropic;  this  character  being 
"linked"  with  a  characteristic  "tan"  color. 

Muscle  Tension  Theory. — Experiments  by  Professor  S.  J.  Holmes 
with  water  scorpions  (Ranatra)  showed  that  when  the  insect  is  illuminated 
from  the  right  side  the  legs  on  the  right  side  are  flexed  and  those  of  the  left 
side  are  extended,  with  a  resultant  locomotion  toward  the  light.  These 
and  other  experiments  "leave  no  doubt  that  the  primary  effects  of  light 
consist  in  changes  in  the  tension  of  muscles."  (Loeb.)  The  muscle  tone 
is  dependent  upon  the  intensity  of  the  light.  If  a  positively  phototropic 
insect  is  illuminated  from  one  side  only  it  turns  toward  the  light  until  the 
muscle  tension  is  equal  on  the  two  sides  of  the  body;  then  locomotion  is 
inevitably  toward  the  source  of  light.  The  stimulus  is  received  through 
the  eyes. 

Artificial  Heliotropic  Machine.— As  illustrating  the  purely 
mechanical  nature  of  the  response  to  light,  the  artificial  heliotropic 
machine,   as  described  by  Loeb,   may  be  referred  to.     Briefly,  this 


312  ENTOMOLOGY 

electrically-operated  machine,  invented  by  Mr.  John  Hays  Hammond, 
Jr.,  is  a  box  containing  the  mechanism  and  mounted  on  three  wheels. 
Two  of  these  are  geared  to  a  driving  motor  and  the  third,  on  the  rear 
end,  can  be  turned  by  means  of  electro-magnets  in  a  horizontal  plane. 
A  pair  of  five-inch  condensing  lenses  on  the  front  end  look  hke  large 
eyes.  If  a  portable  electric  Hght,  as  a  hand  flashhght,  be  turned  on 
in  front  of  the  machine  this  will  immediately  move  toward  the  light  and 
will  follow  the  light  all  around  the  room  in  complex  manoeuvers  at  a 
speed  of  about  three  feet  per  second.  Upon  shading  or  switching 
off  the  light  the  "dog,"  as  it  is  called,  can  be  stopped  at  once,  but  will 
resume  its  uncanny  movements  as  soon  as  the  light  reaches  the  "eyes" 
of  the  machine  in  sufficient  intensity.  The  orientation  mechanism 
possesses  two  selenium  cells,  one  behind  each  "eye,"  which  when  influ- 
enced by  light  effect  the  control  of  sensitive  relays,  analogous  to  the  nerv- 
ous system  of  a  moth.  These  relays  operate  electro-magnetic  switches, 
which  control  the  driving  motors  and  the  steering  wheel. 

The  principle  of  this  mechanism  has  been  applied  to  the  "Hammond 
dirigible  torpedo." 

Thermotropism. — Ants  are  strongly  thermotropic;  they  carry  their 
eggs,  larvae  and  pupae  from  a  cooler  to  a  warmer  place  or  vice  versa, 
and  thus  secure  optimum  conditions  of  temperature.  Caterpillars  and 
cockroaches  migrate  to  regions  of  optimum  temperature. 

In  thermotropism  it  appears  that  the  direction  of  heat  rays  has 
little  or  no  effect  as  compared  with  differences  of  intensity. 

Tropisms  in  General. — Other  kinds  of  tropisms  are  known,  for 
example,  tonotropism,  or  the  control  of  the  direction  of  locomotion 
by  density,  and  electrotropism  {galvanotropism) ;  not  to  mention  any 
more. 

All  these  phenomena  are  responses  of  protoplasm  to  definite  stimuli 
and  are  almost  as  inevitable  as  the  response  of  a  needle  to  a  magnet. 

The  tropisms  of  the  lower  organisms  have  been  experimented  upon 
by  many  skilled  investigators,  whose  results  furnish  a  broad  basis  for 
the  study  of  the  subject  in  the  higher  animals.  Even  in  the  simplest 
organisms,  behavior  is  the  resultant  effect  of  several  or  many  stimuli 
acting  at  once,  and  the  precise  effect  of  each  stimulus  can  be  ascertained 
only  by  the  most  guarded  kind  of  experimentation;  while  in  the  higher 
animals,  with  their  complex  organization,  including  speciahzed  sense 
organs,  the  study  of  behavior  becomes  intricate  and  cannot  be  carried 
on  intelligently  without  an  extensive  knowledge  of  the  behavior  of  uni- 
cellular organisms.     The  properties  of  protoplasm  are  the  key  to  the 


INSECT   BEHAVIOR  313 

behavior  of  organisms.  Furthermore,  the  study  of  tropic  reactions  is 
complicated  by  the  fact  that  they  are  due  not  only  to  external  stimuli, 
but  also  to  Httle-understood  internal  stimuli,  arising  from  unknown 
conditions  of  the  alimentary  canal,  muscles,  reproductive  organs,  etc. 

A  recognized  property  of  protoplasm  is  that  of  adaptation,  as  mani- 
fested in  the  acclimatization  of  protoplasm  to  untoward  conditions 
of  temperature,  hght,  contact  and  other  stimuH;  and  this  adaptation  to 
unusual  conditions  may  take  place  without  the  aid  of  natural  selection. 

A  tropic  reaction  occurs,  whether  it  is  to  prove  useful  to  the  organism 
or  not.  Thus  a  lady-bird  beetle  walks  upward,  on  a  branch,  on  a  fence, 
on  one's  finger.  It  walks  upward  as  far  as  possible  and  then  flies  into 
the  air.  If  it  happens  to  reach  the  tip  of  a  twig  and  finds  aphids  there, 
the  beetle  stops  and  feeds  upon  them.  This  adaptive  result  is  in  a  sense 
incidental.  Yet,  upon  the  whole,  tropic  reactions  are  wonderfully  adap- 
tive in  their  results.  Here  natural  selection  is  of  special  value  as  afford- 
ing an  explanation  of  the  phenomena. 

As  Loeb  and  Davenport  have  insisted,  the  mechanical  reactions  to 
gravity,  light,  heat  and  other  influences  determine  the  behavior  of  the 
organism. 

2.  Instinct 

Insects  are  eminently  instinctive;  though  their  automatic  behavior 
is  often  so  remarkably  successful  as  to  appear  rational,  instead  of  purely 
instinctive. 

A  satisfactory  definition  of  "instinct"  seems  to  be  impossible, 
though  some  of  the  characteristics  of  instinctive  behavior  are  quite 
evident. 

Instinct,  as  distinguished  from  reason,  attains  adaptive  ends  without 
prevision  and  without  experience.  For  example,  a  butterfly  selects  a 
particular  species  of  plant  upon  which  to  lay  her  eggs.  Caterpillars  of 
the  same  species  construct  the  same  kind  of  nest,  though  so  isolated  from 
one  another  as  to  exclude  the  possibility  of  imitation.  Every  caterpillar 
that  pupates  accomplishes  the  intricate  process  after  the  manner  of  its 
kind,  without  the  aid  of  experience. 

Instinctive  actions  belong  to  the  reflex  type — they  consist  of  co-or- 
dinated reflex  acts.  A  complex  instinctive  action  is  a  chain,  each  link 
of  which  is  a  simple  reflex  act.  In  fact,  no  sharp  line  can  be  drawn 
between  reflexive  and  instinctive  actions. 

Basis  of  Instinct.— Reflex  acts,  the  elements  from  which  instinctive 
actions  are  compounded,  are  the  inevitable  responses  of  particular  organs 


314  ENTOMOLOGY 

to  appropriate  stimuli,  and  involve  no  volition.  The  presence  of  an 
organ  normally  implies  the  ability  to  use  it.  The  newly  born  butterfly 
needs  no  practice  preliminary  to  flight.  The  process  of  stinging  is 
entirely  reflex;  a  decapitated  wasp  retains  the  power  to  sting,  directing  its 
weapon  toward  any  part  of  the  body  that  is  irritated;  and  a  freshly 
emerged  wasp,  without  any  practice,  performs  the  stinging  movements 
with  greatest  precision. 

As  Whitman  observes,  the  roots  of  instincts  are  to  be  sought  in  the 
constitutional  activities  of  protoplasm. 

Apparent  Rationality. — The  ostensible  rationality  of  behavior 
among  insects,  as  was  said,  often  leads  one  to  attribute  intelligence  to 
them,  even  when  there  is  no  evidence  of  its  existence.  As  an  illustra- 
tion, many  plant-eating  beetles,  when  disturbed,  habitually  drop  to  the 
ground  and  may  escape  detection  by  remaining  immovable.  We 
cannot,  however,  believe  that  these  insects  "feign  death"  with  any  con- 
sciousness of  the  benefit  thus  to  be  derived.  This  act,  widespread 
among  animals  in  general,  is  instinctive,  or  reflex,  as  Whitman  maintains, 
being  at  the  same  time,  one  of  the  simplest,  most  advantageous  and 
deeply  seated  of  all  instinctive  performances. 

Take  the  many  cases  in  which  an  insect  lays  her  eggs  upon  only  one 
species  of  plant.  The  philenor  butterfly  hunts  out  Aristolochia,  which 
she  cannot  taste,  in  order  to  serve  larvae,  of  whose  existence  she  can  have 
no  foreknowledge.  Oviposition  is  here  an  instinctive  act,  really  a 
chemotropism,  which  is  not  performed  until  it  is  evoked  by  some  sort 
of  stimulus — probably  an  olfactory  one — from  a  particular  kind  of  plant. 

Stimuli. — Some  determinate  sensory  stimulus  is,  indeed,  the  neces- 
sary incentive  to  any  reflex  act.  The  first  movements  of  a  larva  within 
the  egg-shell  are  doubtless  due  to  a  sensation,  probably  one  of  tem- 
perature. Simple  contact  with  the  egg-shell  is  probably  sufficient  to 
stimulate  the  jaws  to  work,  and  the  caterpillar  eats  its  way  out;  yet  it 
cannot  foresee  that  its  biting  is  to  result  in  its  liberation.  Nor,  later  on, 
when  voraciously  devouring  leaves,  can  the  caterpillar  be  supposed  to 
know  that  it  is  storing  up  a  reserve  supply  of  food  for  the  distant  period 
of  pupation  and  the  subsequent  imaginal  stage.  The  ends  of  these 
reflex  actions  are  proximate  and  not  ultimate,  except  from  the  stand- 
point of  higher  intelhgence. 

Just  as  simple  reflexes  link  together  to  form  an  instinctive  action,  so 
may  instincts  themselves  combine.  The  complex  behavior  of  a  solitary 
wasp  is  a  chain  of  instincts,  as  the  Peckhams  have  shown.  All  the  opera- 
tions of  making  the  nest,  stinging  the  prey,  carrying  it  to  the  nest,  etc.. 


INSECT    BEHAVIOR  315 

are  performed  as  a  rule  in  a  definite,  predicable  sequence,  and  even  a 
slight  interference  with  the  normal  sequence  disconcerts  the  insect. 
Just  as  the  performance  of  one  reflex  act  may  serve  as  the  stimulus  for 
the  next  reflex  in  order,  so  the  completion  of  one  instinctive  action  may 
be  in  part  the  stimulus  for  the  next  one. 

Modification  of  Instincts. — An  action  can  be  regarded  as  purely 
instinctive  in  its  initial  performance  only,  because  every  subsequent 
performance  may  have  been  modified  by  experience;  in  other  words, 
habits  may  have  been  forming  and  fixing,  so  that  the  results  of  instinct 
become  blended  with  those  of  experience.  Thus  the  first  flight  of  a 
dragon  fly  is  instinctive  and  erratic,  but  later  efforts,  aided  by  experience, 
are  well  under  control. 

When  once  shaped  by  experience,  reflex  or  instinctive  actions  tend 
to  become  intense  habits.  Thus,  certain  caterpillars,  having  eaten  all 
the  available  leaves  of  a  special  kind,  will  almost  invariably  die  rather 
than  adopt  a  new  food  plant,  whereas  larvae  of  the  same  species  will  eat- 
a  strange  plant  if  it  is  offered  to  them  at  birth.  An  act  is  strengthened 
in  each  repetition  by  the  influence  of  habit,  to  the  increasing  exclusion 
of  other  possible  modes  of  action.  Many  a  caterpillar,  having  eaten  its 
way  out  of  the  egg-shell,  does  not  stop  eating,  but  consumes  the  remain- 
der of  the  shell — a  reflex  act,  started  by  a  stimulus  of  contact  against  the 
jaws  and  continued  until  the  cessation  of  the  stimulus,  unless  some 
stronger  stimulus  should  intervene.  It  has  been  said  that  the  larva  eats 
the  remains  of  the  shell  because  they  might  betray  its  presence  to  its 
enemies.  Whether  this  is  true  or  not,  to  assume  conscious  foresight  of 
such  a  result  on  the  part  of  an  inexperienced  caterpillar  is  worse  than 
unnecessary. 

With  insects,  as  with  other  animals,  many  instincts  are  transitory; 
even  when  partially  fixed  by  habit,  they  are  replaceable  by  stronger 
instincts.  Thus  the  gregarious  habit  of  larvae  is  finally  overpowered  by 
a  propensity  to  wander,  which  does  not  mature,  however,  until  the 
approach  of  the  transformation  period.  The  reproductive  instinct  is 
another  of  those  impulses  that  do  not  ripen  until  a  certain  age  in  the 
individual. 

Inflexibility  of  Instincts. — Broadly  speaking,  instinctive  actions 
lack  individuality — are  performed  in  the  same  way  by  every  individual 
of  the  species.  The  solitary  wasps  of  the  same  species  are  remarkably 
consistent  in  architecture,  in  the  selection  of  a  special  kind  of  prey,  in 
the  way  they  sting  it,  carry  it  to  the  nest  and  dispose  of  it;  all  these 
operations,  moreover,  are  performed  in  a  sequence  that  is  characteristic 


3l6  ENTOMOLOGY 

of  the  species.  Examples  of  this  so-called  inflexibility  of  instinct  are 
so  omnipresent,  indeed,  that  insect  behavior  as  a  whole  is  admitted  to 
be  instinctive,  or  automatic.  Insects  are  capable  of  an  immense  num- 
ber of  reflex  impulses,  ready  to  act  singly  or  in  intricate  correlation, 
upon  the  requisite  stimuli  from  the  environment. 

To  normal  conditions  of  the  environment,  the  behavior  of  an  insect 
is  accurately  adjusted;  but  in  the  face  of  abnormal  circumstances 
demanding  the  exercise  of  judgment,  most  insects  are  helpless.  The 
speciahzation  to  one  kind  of  food,  though  usually  advantageous,  is  fatal 
if  the  supply  becomes  insufiicient  and  the  larva  is  unable  to  adopt 
another  f  ood .  A  species  of  Sphex  habitually  drags  its  grasshopper  victim 
by  one  antenna.  Fabre  cut  off  both  antennae  and  then  found  that  the 
wasp,  after  vain  efforts  to  secure  its  customary  hold,  abandoned  the 
prey.  Under  such  unaccustomed  conditions,  insects  often  show  a  sur- 
prising stupidity,  capable  as  they  are  amid  ordinary  circumstances. 

Flexibility  of  Instincts. — Notwithstanding  such  examples,  the 
common  assertion  that  instincts  are  absolutely  "blind,"  or  inflexible,  is 
incorrect.  Instinctive  acts  are  not  mechanically  invariable,  though 
their  variations  are  so  inconspicuous  as  frequently  to  escape  casual 
observation.  A  precise  observer  can  detect  individual  variations  in  the 
performance  of  any  instinctive  act — variations  analogous  to  those  of 
structure. 

To  take  extreme  examples,  the  Peckhams  found  that  an  occasional 
queen  of  Polistes  fusca  would  occupy  a  comb  of  the  previous  year, 
instead  of  building  a  new  one ;  and  that  an  individual  of  Pompilus  mar- 
ginatus,  instead  of  hiding  her  captured  spider  in  a  hole  or  under  a  lump 
of  earth  as  usual,  hung  it  up  in  the  fork  of  a  purslane  plant.  They 
observed  also  that  one  Ammophila,  in  order  to  pound  down  the  earth 
over  her  nest,  actually  used  a  stone,  held  between  the  mandibles  (Fig. 
297). 

This  performance,  which  has  been  witnessed  also  by  Professor 
Williston  and  a  few  other  observers,  illustrates  the  flexibihty  of  in- 
stinctive action,  and  has  been  cited  as  an  instance  of  adaptability,  or 
intelligence.  It  can  not  be  supposed,  however,  that  the  insect  is 
conscious  of  the  efficiency  of  a  stone  as  a  tool.  The  performance  may  be 
an  accident.  If  one  observes  an  Ammophila  at  work  he  will  notice  that 
she  not  only  pounds  down  the  earth  with  her  head,  but  also  lifts  and 
lays  aside  small  stones  with  her  mandibles.  Possibly  she  now  and  then 
chances  to  begin  the  pounding  movement  before  she  has  happened  to 
release  a  stone  from  her  jaws. 


INSECT   BEHAVIOR  317 

Even  the  despotic  power  of  habit  may  be  overborne  by  individual 
adaptability.  Among  caterpillars  that  have  exhausted  their  customary 
food,  there  are  often  a  few  that  will  adopt  a  new  food  plant  and  survive, 
leaving  their  more  conservative  fellows  to  starve. 

As  Darwin  himself  held,  the  doctrine  of  natural  selection  is  applicable 
to  instincts  as  well  as  structures.  All  reflex  acts  are  to  some  extent 
variable.  Disadvantageous  reflexes  or  combinations  of  reflexes  elimi- 
nate themselves,  while  advantageous  ones  persist  and  accumulate. 

Indeed,  structures  and  instincts  must  frequently  have  evolved  hand 
in  hand.     The  remarkable  protective  resemblance  of  the  Kallima  butter- 


FiG.   297. — Ammophila  urnaria  using  a  stone  to  pound  down  the  earth  over  her  nest. 
Greatly  enlarged. — After  Peckham,  from   Bull.    Wisconsin  Geol.  and  Nat.  Hist.  Survey. 


fly  would  be  useless,  did  not  the  insect  instinctively  rest  among  dead 
leaves  of  the  appropriate  kind. 

Origin  of  Instinct. — There  are  two  leading  theories  as  to  the  origin 
of  instinct.  Lamarck,  Romanes  and  their  followers  have  regarded  in- 
stinct as  inherited  habit;  have  supposed  that  instincts  have  originated 
by  the  relegation  to  the  reflex  type  of  actions  that  at  first  were  rational, 
and  that  instincts  represent  the  accumulated  results  of  ancestral  experi- 
ence. This  habit  theory,  however,  has  little  to  support  it,  and  assumes 
the  inheritance  of  acquired  characters — which  has  not  been  proved. 

The  selection  theory  of  Darwin,  Weismann,  Morgan  and  others  has 
much  in  its  favor.  It  regards  reflex  acts  as  primitive,  as  the  raw 
material  from  which  natural  selection,  as  the  chief  factor,  has  effected 
those  combinations  that  are  termed  instincts. 


3l8  ENTOMOLOGY 

Instincts  and  Tropisms. — We  have  already  emphasized  the  fact 
that  an  instinct  is  a  reflex  act  or  a  combination  of  reflex  acts.  The  same 
fact  may  now  be  stated  in  these  words:  an  instinct  is  a  tropism  or  a 
combination  of  tropisms.  The  more  important  of  these  tropisms  have 
been  considered.  Whenever  possible  it  is  better  to  discard  the  ambigu- 
ous term  instinct  in  favor  of  such  more  precise  terms  as  phototropism, 
geotropism,  etc.;  though  the  term  instinct  remains  useful  as  applied  to  an 
action  that  is  the  resultant  of  several  tropic  responses. 

The  modern  student  of  instincts  aims  to  resolve  them  into  their 
component  reflexes  and  to  determine  as  precisely  as  possible  the  influ- 
ence of  each  reflex  component.  Thanks  to  the  labors  of  a  great  number 
of  skilled  investigators,  we  are  no  longer  satisfied  to  class  an  action  as 
"instinctive"  and  then  dismiss  it  from  thought;  for  we  are  now  in  a 
position  to  analyze  the  action,  and  may  hope  to  explain  it  eventually 
in  terms  of  the  physical  and  chemical  properties  of  protoplasm. 

3.  Intelligence 

Though  manifestly  dominant,  pure  instinct  fails  to  account  for  all 
insect  behavior.  The  abihty  of  an  insect  to  profit  by  experience  indi- 
cates some  degree  of  intelligence. 

Take,  for  example,  the  precision  with  which  bees  or  wasps  find  their 
way  back  to  the  nest.  This  is  no  longer  to  be  accounted  for  on  the  as- 
sumption of  a  mysterious  "sense  of  direction,"  for  there  is  the  best  of 
evidence  for  believing  that  it  depends  upon  the  recognition  of  surround- 
ing objects.  When  leaving  the  nest  for  the  first  time,  these  insects  make 
"locality  studies,"  which  are  often  elaborate.  Referring  to  a  digger- 
wasp,  Sphex  ichneumonea,  the  Peckhams  write:  "At  last,  the  nest  dug, 
she  was  ready  to  go  out  and  seek  for  her  store  of  provision  and  now  came 
a  most  thorough  and  systematic  study  of  the  surroundings.  The  nests 
that  had  been  made  and  then  deserted  had  been  left  without  any 
circling.  Evidently  she  was  conscious  of  the  difference  and  meant, 
now,  to  take  all  necessary  precautions  against  losing  her  way.  She 
flew  in  and  out  among  the  plants  first  in  narrow  circles  near  the  surface 
of  the  ground,  and  now  in  wider  and  wider  ones  as  she  rose  higher  in  the 
air,  until  at  last  she  took  a  straight  line  and  disappeared  in  the  distance. 
The  diagram  [Fig.  298,  A]  gives  a  tracing  of  her  first  study  preparatory 
to  departure.  Very  often  after  one  thorough  study  of  the  topography 
of  her  home  has  been  made,  a  wasp  goes  away  a  second  time  with  much 
less  circling  or  with  none  at  all.  The  second  diagram  [Fig.  298,  B]  gives 
a  fair  illustration  of  one  of  these  more  hasty  departures.     , 


INSECT   BEHAVIOR 


319 


"If  the  examination  of  the  objects  about  the  nest  makes  no  impres- 
sion upon  the  wasp,  or  if  it  is  not  remembered,  she  ought  not  to  be 
inconvenienced  nor  thrown  of!  her  track  when  weeds  and  stones  are 
removed  and  the  surface  of  the  ground  is  smoothed  over;  but  this  is 
just  what  happens.  Aporus  fasciatus  entirely  lost  her  way  when  we 
broke  off  the  leaf  that  covered  her  nest,  but  found  it  without  trouble 
when  the  missing  object  was  replaced.  All  the  species  of  Cerceris  were 
extremely  annoyed  if  we  placed  any  new  object  near  their  nesting-places. 
Our  Ammophila  refused  to  make  use  of  her  burrow  after  we  had  drawn 


Fig.  298. — Locality  studies  made  by  a  wasp,  Sphex  ichneumonea.  A,  a  thorough  study; 
B,  a  hasty  study;  «,  nest. — After  Peckham,  from  Bull.  Wisconsin  Geol.  and  Nat.  Hist. 
Survey. 

some  deep  Hnes  in  the  dust  before  it.  The  same  annoyance  is  exhibited 
when  there  is  any  change  made  near  the  spot  upon  which  the  prey  of 
the  wasp,  whatever  it  may  be,  is  deposited  temporarily." 

If  we  take,  as  one  criterion  of  inteUigence,  the  power  to  choose  be- 
tween alternatives,  then  insects  are  more  inteUigent  than  is  generally 
admitted.  The  control  of  locomotion,  the  selection  of  prey,  and  the 
avoidance  of  enemies,  as  results  of  experience,  indicate  powers  of  dis- 
crimination. The  power  of  intercommunication,  conceded  to  exist 
among  social  Hymenoptera,  implies  some  degree  of  intelligence. 

If  instinct  is  bhnd,  or  mechanical,  with  no  adjustment  of  means  to 
ends,  then  a  pronounced  individuality  of  action  must  signify  something 
more  than  instinct.  In  regard  to  a  female  Pompilus  scelestus,  which  had 
dragged  a  large  spider  nearly  to  her  nest,   the  Peckhams  observe: 


320 


ENTOMOLOGY 


"presently  she  went  to  look  at  her  nest  and  seemed  to  be  struck  with  a 
thought  that  had  already  occurred  to  us — that  it  was  decidedly  too 
small  to  hold  the  spider.  Back  she  went  for  another  survey  of  her 
bulky  victim,  measured  it  with  her  eye,  without  touching  it,  drew  her 
conclusions,  and  at  once  returned  to  the  nest  and  began  to  make  it  larger. 
We  have  several  times  seen  wasps  enlarge  their  holes  when  a  trial  had 
demonstrated  that  the  spider  would  not  go  in,  but  this  seemed  a  remark- 
ably intelligent  use  of  the  comparative  faculty." 

From  the  standpoint  of  pure  instinct,  indeed,  much  of  the  behavior 
of  the  solitary  wasps  is  inexplicable;  while  the  actions  of  the  social 
Hymenoptera  have  led  some  of  the  most  critical  students  to  ascribe 
intelligence  to  these  insects.  The  activities  of  the  harvesting  ants,  the 
miHtary  or  the  slave-holding  species,  are  of  such  a  nature  that  the 
possibility  of  education  by  experience  and  instruction  is  strong,  to  say 
the  least.  In  fact,  Forel  has  maintained  that  a  young  ant  is  actually 
trained  to  its  domestic  duties  by  its  older  companions. 

In  his  scholarly  volume,  Ants,  Wheeler  shows  that  these  insects 
have  the  ability  tcr  profit  by  experience,  as  exhibited  in  their  foraging 
and  homing  operations,  the  recollection  of  nest-mates  and  aliens, 
communication,  imitation  and  co-operation;  and  that  they  have 
memory  in  the  general  sense  of  the  word,  but  that  they  have  memory 
images  only  as  the  result  of  sensory  stimulation,  and  are  unable  to  call 
them  up  at  will,  much  less  to  refer  them  to  the  absent  or  to  the  past. 
"If  this  moderate  estimate  of  the  memory  of  ants  be  correct,  it  follows 
that  they  must  be  incapable  of  reasoning — of  'focusing  the  wherefore,' 
to  use  Lloyd  Morgan's  expression,  for  a  mere  association  of  sense  impres- 
sions is  not  deducing  conclusions  from  premises."     (Wheeler.) 

It  is  extremely  difl&cult,  if  not  impossible,  however,  to  draw  the  line 
between  instinct  and  intelUgence;  and  in  doubtful  cases  there  is  a  gen- 
eral tendency  to  exaggerate  the  importance  of  intelligence  rather  than 
that  of  instinct.  For  example,  the  well-known  discrimination  on  the  part 
of  ants  between  members  of  their  own  colony  and  those  of  other  colonies, 
even  of  the  same  species,  would  seem  to  imply  intelligent  recognition. 
This  recognition  is  due,  however,  to  a  characteristic  odor,  which 
is  derived  from  the  mother  of  the  community.  An  ant  after  being  washed 
receives  hostile  treatment  from  others  in  its  own  colony;  while  an  alien 
ant  after  being  smeared  with  the  juices  of  hostile  ants  is  treated  by  the 
latter  as  a  friend. 

Each  instance  of  apparent  intelligence  must  be  examined  impartially 
on  its  own  merits.     At  present  it  may  be  said  that,  while  most  of  the 


INSECT   BEHAVIOR  32I 

behavior  of  insects  is  purely  instinctive,  there  is  some  reason  to  believe 
that  at  least  gleams  of  intelligence  appear  in  the  most  speciahzed 
Hymenoptera. 

Lack  of  Rationality.- — However  intelligent  the  social  Hymenoptera 
may  be  in  their  way,  they  show  no  signs  of  the  power  of  abstract  reasoning. 
Even  ants,  according  to  the  experiments  of  Lubbock,  display  profound 
stupidity  in  the  face  of  novel  emergencies  from  which  they  might 
extricate  themselves  by  abstract  reasoning  of  the  simplest  kind.  The 
thoughts  of  an  ant  or  bee  seem  to  be  limited  to  simple  associations  of 
concrete  things.  Miss  Enteman  observed  a  Polistes  worker  which 
gnawed  a  piece  out  of  the  side  of  a  dead  larva  of  its  own  kind  and,  turn- 
ing, actually  offered  it  as  food  to  the  mouth  of  the  same  larva.  In 
another  instance  a  larva  was  attacked  and  killed,  and  then  offered  a 
piece  of  its  own  body. 

Such  examples  as  these  emphasize  the  strength  of  the  reflex  factor  in 
the  behavior  of  insects.  Indeed,  the  basis  of  all  behavior  is  being  sought 
in  the  reactions  of  protoplasm  to  external  stimuli.  Possibly  even  mem- 
ory, consciousness  and  other  attributes  of  intelhgence  will  eventually  be 
reduced  to  this  basis,  improbable  as  it  may  now  seem.  • 


CHAPTER  XII 

DISTRIBUTION 

I.  Geographical 

Importance  of  Dispersion. — Dispersion  enables  species  to  miti- 
gate the  intense  competition  and  the  rigid  selection  that  result  from 
crowded  numbers;  hence  the  tendency  to  disperse,  being  self -preserva- 
tive, has  become  universal.  Some  species  habitually  emigrate  in  pro- 
digious numbers:  the  African  migratory  locust,  the  Rocky  Mountain 
locust,  and  the  milkweed  butterfly,  which  annually  leaves  the  Northern 
states  for  the  South  in  immense  swarms,  in  autumn,  and  in  the  follow- 
ing spring  straggles  back  to  the  North.  Vanessa  cardui  occasionally 
migrates  in  immense  numbers,  as  do  also  Fieri s,  some  dragon  flies  and 
some  beetles,  notably  CoccinelHdae. 

Wide  Distribution  of  Insects. — Insects  have  been  found  in  almost 
every  latitude  and  altitude  explored  by  man.  Butterflies  and  mos- 
quitoes occur  beyond  the  polar  circle,  the  former  in  Lat.  83°  N.,  the 
latter  in  Lat.  72°  N.,  and  a  species  of  Emesa  closely  aUied  to  our  common 
E.  longipes  is  recorded  by  Whymper  from  an  altitude  of  16,500  ft.  in 
Ecuador,  where,  according  to  the  same  traveler,  Orthoptera  occur  at 
16.000  ft.,  Pieris  xanthodice  ranges  above  15,000  ft.,  and  dragon  flies, 
Hymenoptera  and  scorpions  reach  a  height  of  12,000  ft.,  while  twenty- 
nine  species  of  Lepidoptera  range  upward  of  7,300  ft.  A  very  few 
species  of  insects  inhabit  salt  water,  Halobates  being  found  far  at  sea; 
some  kinds  live  in  arid  regions  and  a  few  even  in  hot  springs,  while 
caves  furnish  many  pecuhar  species.  In  short,  insects  are  the  most 
widely  distributed  of  all  animals,  excepting  Protozoa  and  possibly 
Mollusca. 

While  all  the  large  orders  of  insects  are  world-wide  in  distribution, 
the  most  richly  distributed  are  Coleoptera,  Thysanura  and  Collembola, 
the  last  two  feeding  usually  upon  minute  particles  of  organic  matter  in 
the  soil  and  being  remarkably  tolerant  of  extremes  of  temperature. 
The  four  chief  families  of  butterflies  occur  the  world  over,  as  do  several 
families  of  beetles.  Of  species  that  are  essentially  cosmopoHtan  we  may 
mention  the  coWemholsm  Folsofnia  fimetaria,  and  the  butterflies  Vanessa 
cardui  and  Anosia  plexippus,  while  among  beetles  no  less  than  one  hun- 

322 


DISTRIBUTION  323 

dred  species  are  cosmopolitan  or  subcosmopolitan,  including  Tenehrio 
molitor,  Silvanus  surinamensis,  Dermestes  lardarius,  Attagenus  piceus 
and  Calandra  oryza.  The  coccinellid  genus  Scymnus  occurs  in  North 
America,  Europe,  Hawaii,  Galapagos  Islands  and  New  Zealand,  and 
Anohium  and  Hydrobius  are  distributed  as  widely.  The  huge  noctuid, 
Erebus  odora,  occurring  in  Brazil  on  the  lowlands,  and  in  Ecuador  at  an 
altitude  of  10,000  ft.,  finds  its  way  up  into  the  United  States  and  even 
into  Canada.  The  chinch  bug  and  many  other  Central  American  forms 
also  spread  far  northward,  as  described  beyond. 

Means  of  Dispersal. — This  exceptional  range  of  insects  is  due  to 
their  exceptional  natural  advantages  for  dispersal,  chief  among  which 
are  the  power  of  flight  and  the  ability  to  be  carried  by  the  wind.  The 
migratory  locust,  Schistocerca  peregrina,  has  been  found  on  the  wing  five 
hundred  miles  east  of  South  America.  The  home  of  the  genus,  accord- 
ing to  Scudder,  is  Mexico  and  Central  America,  where  23  species  are 
found;  20  occurring  in  South  America,  including  the  Galapagos  Islands, 
II  in  the  United  States  and  6  in  the  West  Indies;  and  there  is  every 
reason  to  believe  that  S.  peregrina — the  biblical  locust  and  the  only 
representative  of  its  genus  in  Africa — crossed  over  from  South  America, 
where  it  is  found  indeed  at  present.  Darwin  and  others  have  recorded 
many  instances  of  insects  being  taken  alive  far  at  sea;  Trimen  mentions 
moths  and  longicorn  beetles  as  occurring  230  miles  west  of  the  African 
coast  and  Sphinx  convolvulus  as  flying  aboard  ship  420  miles  out.  In 
these  instances  the  insects  have  usually  been  assisted  or  carried  by 
strong  winds,  particularly  the  trade-winds,  and  oceanic  islands  have 
undoubtedly  been  colonized  in  this  way.  On  land,  Webster  has  found 
that  the  direction  in  which  the  Hessian  fly  spreads  is  determined  largely 
by  the  prevailing  winds  at  the  time  when  these  delicate  insects  are  on 
the  wing,  and  that  the  San  Jose  scale  insect  spreads  far  more  rapidly 
with  the  prevailing  winds  than  against  them,  the  wind  carrying  the 
larvae  as  if  they  were  so  many  particles  of  dust.  The  pernicious  buffalo- 
gnat  of  the  South  emerges  from  the  waters  of  the  bayous  and  may  be 
carried  on  a  strong  wind  to  appear  suddenly  in  enormous  numbers 
twenty  miles  distant  from  its  breeding  place.  Mosquitoes  are  dis- 
tributed locally  by  Hght  breezes,  but  chng  to  the  herbage  during  strong 
winds. 

Ocean  currents  may  carry  eggs,  larvae  or  adults  on  vegetable  drift 
to  new  places  thousands  of  miles  away.  Thus  the  Gulf  Stream  annually 
transports  thousands  of  tropical  insects  to  the  shores  of  Great  Britain, 
where  they  do  not  survive,  however. 


324  ENTOMOLOGY 

Fresh-water  streams  convey  incalculable  numbers  of  insects  in  all 
stages;  and  insects  as  a  whole  are  very  tenacious  of  life,  being  able  to 
withstand  prolonged  immersion  in  water,  and  even  freezing,  in  many 
instances,  while  they  can  hve  for  a  long  time  without  food. 

The  universal  process,  of  soil-denudation  must  aid  the  diffusion  of 
insects,  slowly  but  constantly. 

Birds  and  mammals  disseminate  various  insects  in  one  way  or 
another,  while  the  agency  of  man  is,  of  course,  highly  important.  In- 
tentionally, he  has  spread  such  useful  species  as  the  honey  bee,  the  silk- 
worm and  certain  useful  parasites;  incidentally  he  has  distributed  the 
San  Jose  scale,  Colorado  potato  beetle,  gipsy  moth  and  many  other 
pests. 

Barriers. — The  most  important  of  the  mechanical  barriers  which 
limit  the  spread  of  terrestrial  species  is  evidently  the  sea.  Mountain 
ranges  retard  distribution  more  or  less  successfully,  though  a  species 
may  spread  along  one  side  of  a  range  and  sooner  or  later  pass  through  a 
break  or  else  around  one  end.  Mountain  chains  act  as  barriers, 
however,  chiefly  because  they  present  unendurable  conditions  of 
climate  and  vegetation.  For  the  same  reason  deserts  are  highly  effect- 
ive barriers.  Indeed  the  most  important  checks  upon  distribution  are 
those  of  climate,  and  of  cUmatal  factors  temperature  is  the  most  power- 
ful. Tropical  species  cannot,  as  a  rule,  survive  and  reproduce  in 
regions  of  frost;  most  of  the  tropical  species  which  have  entered  the 
United  States  are  restricted  to  its  narrow  tropical  belts  (Plate  IV). 
The  stages  of  an  insect  are  frequently  so  accurately  adjusted  to  par- 
ticular climatal  conditions  that  an  unfamiliar  climate  deranges  the  life 
cycle.  Thus  many  Southern  butterflies  find  their  way  every  year  to 
the  Northern  states,  only  to  perish  without  reproducing  their  kind. 
Insects  are,  nevertheless,  more  adaptable  than  most  other  animals  in 
respect  to  climate,  and  frequently  follow  their  food  plants  into  new 
climates,  as  in  the  case  of  the  harlequin  cabbage  bug,  which  has  pushed 
north  from  the  tropics  to  Missouri,  southern  Ilhnois  and  Indiana. 

Humidity  ranks  next  to  temperature  in  the  importance  of  its 
influence  upon  the  distribution  of  organisms,  but  in  the  case  of  animals 
acts  for  the  most  part  indirectly,  by  its  effects  upon  vegetation.  Thus 
the  effectiveness  of  an  arid  region  as  a  barrier  is  due  chiefly  to  the  lack  of 
vegetation  in  consequence  of  the  lack  of  moisture.  Excessive  moisture, 
on  the  other  hand,  may  act  as  a  barrier.  The  Rocky  Mountain  locust, 
which  formerly  migrated  eastward  in  immense  swarms,  succumbed  in  the 
moist  valley  of  the  Mississippi;  the  chinch  bug  is  never  seriously  injur- 


DISTRIBUTION  325 

ous  in  wet  years.  Moisture  checks  the  development  of  these  and  other 
insects  in  ways  as  yet  unascertained;  possibly  it  acts  indirectly  by  favor- 
ing the  growth  of  fungus  diseases,  to  which  insects  are  much  subject. 

The  absence  of  proper  food  is  more  effective  than  climate,  as  a  direct 
check  upon  the  spread  of  an  animal;  food  itself  being,  of  course,  de- 
pendent ultimately  upon  climatal  factors  and  soil.  Many  insects,  being 
confined  to  a  single  food  plant,  can  not  exist  long  where  this  plant  does 
not  occur ;  but  they  will  follow  the  plant,  as  was  just  said,  into  new 
climates;  thus  Anosia  plexippus  is  following  the  milkweed  over  the 
world.  The  butterfly  Euphydryas  phaeton  is  remarkably  local  in  its 
occurrence,  being  limited  to  swamps  where  its  chief  food  plant  {Chelone 
glabra)  grows ;  and  Epidemia  epixanthe  is  similarly  restricted  to  cranberry 
bogs. 

Former  Highways  of  Distribution. — Many  facts  of  distribution 
which  are  inexplicable  under  the  present  conditions  of  topography  and 
climate  become  intelHgible  in  the  Hght  of  geological  history.  The 
marked  similarity  between  the  fauna  of  Europe  and  that  of  North 
America  means  community  of  origin;  and  though  the  Arctic  zone  now 
interposes  as  a  barrier,  there  was  once  an  opportunity  for  free  dispersion 
when,  in  the  early  Pleistocene  or  late  Pliocene,  a  land  connection  existed 
between  Asia  and  North  America  and  a  warm  climate  prevailed 
throughout  what  is  now  the  Arctic  region. 

The  extraordinary  isolation  of  the  butterfly  CEneis  semidea  on  moun- 
tain summits  in  New  Hampshire  and  Colorado  (particularly  Mt. 
Washington,  N.  H.,  and  Pikes  Peak,  Col.)  is  explained  by  glacial  geology. 
The  ancestors  of  this  species,  it  is  thought,  were  driven  southward  be- 
fore an  advancing  ice-sheet  and  then  foflowed  it  back  as  it  retreated 
northward,  adapted  as  they  were  to  a  rigorously  cold  cKmate.  Some 
of  those  ancestors  presumably  followed  the  melting  ice  up  the  mountain 
sides,  until  they  found  themselves  stranded  on  the  summits.  Other 
individuals,  undiverted  from  the  lowlands,  followed  the  retreating  glacier 
into  the  far  north;  and  at  present  there  occurs  throughout  Labrador  a 
species  of  CEneis  which  differs  but  sHghtly  from  its  lonely  ally  of  the 
mountain  tops. 

Glaciation  undoubtedly  had  a  profound  effect  upon  the  fauna  and 
flora  of  North  America.  "With  the  slow  southward  advance  of  the  ice, 
animals  were  crowded  southward;  with  its  recession  they  advanced 
again  northward  to  reoccupy  the  desolated  region,  until  now  it  has  long 
been  repopulated,  either  with  the  direct  descendants  of  its  former  in- 
habitants or  with  such  limitations  to  the  integrity  of  the  fauna  as  this 


326  ENTOMOLOGY 

interruption  of  local  life  may  have  caused."  (Scudder.)  Probably 
many  species  were  exterminated  and  many  others  became  greatly  modi- 
fied, though  little  is  known  as  to  the  relationship  of  the  present  fauna  to 
the  preglacial  fauna.  "The  glacial  cold  still  lingers  over  the  northern 
part  of  this  continent  and  our  present  animals  are  only  a  remnant  of 
the  rich  fauna  that  existed  in  former  ages,  when  the  magnolia  and  the 
sassafras  thrived  in  Greenland." 

Island  Faunae. — The  abihty  of  insects  to  surmount  barriers,  under 
favorable  circumstances,  is  strikingly  shown  in  the  colonization  of 
oceanic  islands.  Not  a  few  insects,  including  Vanessa  cardui,  have 
found  their  way  to  the  isolated  island  of  St.  Helena.  In  the  Madeira 
Islands,  according  to  Wollaston,  there  are  580  species  of  Coleoptera,  of 
which  314  are  known  to  occur  in  Europe,  while  all  the  rest  are  closely 
allied  to  European  forms.  Subtracting  120  species  as  having  been  intro- 
duced probably  or  possibly  through  the  agency  of  man,  there  remain 
194  that  have  been  introduced  by  "natural"  means.  The  rest,  266 
species,  are  endemic,  though  akin  to  European  species. 

The  scanty  insect  fauna  of  the  Galapagos  Islands  includes  twenty 
species  of  Orthoptera,  which  have  been  studied  by  Scudder  and  by  Snod- 
grass.  Five  of  these  are  cosmopolitan  cockroaches,  doubtless  intro- 
duced commercially,  and  the  remaining  fifteen  are  all  "distinctly  South 
and  Central  American  in  their  affinities."  Three  of  these  fifteen  are 
strong-winged  species  which  doubtless  arrived  by  flight  from  the  neigh- 
boring mainland;  indeed,  Scudder  records  a  Schistocerca  {S.  exsul)  as 
having  been  taken  at  sea  two  hundred  miles  off  the  west  coast  of  South 
America,  or  nearly  half  way  to  the  Galapagos  Islands.  Thirteen  of  the 
fifteen  are  endemic,  and  five  are  apterous  or  subapterous,  while  a  sixth 
has  an  apterous  female.  Apterous  insects,  noticeably  common  on 
wind-swept  oceanic  islands,  may  have  been  carried  thither  on  drift- 
wood, though  it  is  more  likely  that  the  apterous  condition  arose  on  the 
islands,  where  the  better-winged  and  more  venturesome  individuals  may 
.have  been  constantly  swept  out  to  sea  and  drowned,  leaving  the  more 
feeble-winged  and  less  venturesome  individuals  behind,  to  reproduce 
their  own  life-saving  peculiarities. 

The  Coleoptera  of  the  Hawaiian  Islands,  studied  by  Dr.  Sharp,  num- 
ber 428  species,  representing  38  famihes,  and  "are  mostly  small  or  very 
minute  insects,"  the  few  large  forms  being  non-endemic,  with  little  or 
no  doubt;  352  species  are  at  present  known  only  from  this  archipelago. 
Dr.  Sharp  distinguishes  three  elements  in  the  fauna:  "first,  species  that 
have  been  introduced,  in  all  probabiUty  comparatively  recently,  by  arti- 


DISTRIBUTION  327 

ficial  means,  such  as  with  provisions,  stores,  building  timber,  ballast,  or 
growing  plants;  many  of  these  species  are  nearly  cosmopolitan.  Second, 
species  that  have  arrived  in  the  islands,  and  have  become  more  or  less 
completely  naturalized;  they  are  most  of  them  known  to  be  wood-  or 
bark-beetles,  but  some  that  are  not  so  may  have  come  with  the  earth 
adhering  to  the  roots  of  floating  trees;  a  few,  such  as  the  Dytiscidae,  or 
water  beetles,  may  possibly  have  been  introduced  by.  violent  winds. 
Third,  after  making  every  allowance  for  introduction  by  these  artificial 
and  natural  methods,  there  still  remains  a  large  portion  standing  out 
in  striking  contrast  with  the  others,  which  we  are  justified  in  considering 
strictly  endemic  or  autochthonous."  Among  the  introduced  genera  are 
Coccinella,  Dermestes,  Aphodius,  Buprestis,  Ptinus  and  Ceramhyx.  The 
immigrant  longicorns  appear  to  have  been  derived  "from  the  nearest 
lands  in  various  directions" — the  Phihppine  Islands,  tropical  America 
and  the  Polynesian  Islands — and  the  same  conclusion  will  probably  be 
found  to  hold  for  the  other  immigrants,  when  their  general  distribution 
shall  have  been  suj6&ciently  studied.  The  endemic  species  number  214, 
or  exactly  half  the  total  number  of  species,  and  are  distributed  among  9 
families,  as  follows: 

Families.  Species.  Genera.  Endemic 

Genera. 

Carabidae 51  7  7 

Staphylinidae 19  3  i 

Nitidulidae 38  2  i 

Elateridae 7  i  i 

Ptinidas  (Anobiini) 19  3  3 

Cioidae 19  i  o 

Aglycj'deridse 30  i  i 

Curculionidae  (Cossonini) 21  3  3 

Cerambjxidae 10  i  i 

Sharp  writes:  "I  think  it  may  be  looked  on  as  certain  that  these 
islands  are  the  home  of  a  large  number  of  peculiar  species  not  at  present 
existing  elsewhere,  and  if  so  it  follows  that  either  they  must  have  existed 
formerly  elsewhere  and  migrated  to  the  islands,  and  since  have  become 
extinct  in  their  original  homes,  or  that  they  must  have  been  produced 
within  the  islands.  This  last  seems  the  simpler  and  more  probable  sup- 
position, and  it  appears  highly  probable  that  there  has  been  a  large 
amount  of  endemic  evolution  within  the  limits  of  these  isolated  islands." 

The  parasitic  Hymenoptera  of  Hawaii,  according  to  Ashmead,  num- 
ber 14  families,  69  genera  and  128  species;  only  eleven  genera  are  en- 
demic and  most  of  the  other  genera  are  represented  in  nearly  all  the 


328  ENTOMOLOGY 

known  faunae  of  the  earth.  Ashmead  concurs  in  the  view  that  the 
Hawaiian  fauna  was  originally  derived  from  the  Australasian  fauna — 
the  view  held  by  all  the  specialists  who  have  studied  Hawaiian  insects. 

Geographical  Varieties. — Darwin  found  that  wide-ranging  species 
are  as  a  rule  highly  variable.  The  cosmopolitan  butterfly  Vanessa 
cardui  presents  striking  variations  in  different  parts  of  the  earth,  largely 
on  account  of  climatal  differences,  as  is  indicated  by  the  temperature 
experiments  of  several  investigators.  Standfuss  exposed  German  pupae 
of  this  insect  to  cold,  and  obtained  thereby  a  dark  variety  such  as  occurs 
in  Lapland;  and  by  the  influence  of  warmth,  obtained  a  very  pale  form 
such  as  occurs  normally  in  the  tropics  only.  Our  Cyaniris  pseudargi- 
olus,  which  ranges  from  Alaska  into  Mexico  and  from  the  Pacific  to  the 
Atlantic,  exhibits  many  geographical  varieties,  some  of  which  are 
clearly  due  to  temperature,  as  experiments  have  shown. 

Geographical  isolation  is  often  followed  by  changes  in  the  specific 
characters  of  an  organism,  as  witness  the  endemic  species  and  varieties 
of  oceanic  islands.  Even  in  the  same  archipelago,  the  different  islands 
may  be  characterized  by  different  varieties  of  one  and  the  same  species, 
or  even  by  different  but  closely  allied  species  of  the  same  genus.  Thus 
Darwin  and  Alexander  Agassiz  found  that  in  the  Galapagos  Islands  each 
island  had  its  own  species  of  Tropidurus  (a  lizard)  and  had  only  one 
species,  with  almost  no  exceptions.  The  same  phenomenon  occurs  in 
the  two  Galapagan  species  of  Schistocerca — S.  melanocera  and  5", 
literosa.  In  melanocera,  as  Scudder  discovered,  ''Three  or  four  distinct 
types  are  becoming  gradually  differentiated  on  the  eight  [now  ten] 
islands  from  which  they  are  known."  Snodgrass,  who  has  made 
important  additions  to  Scudder's  account,  says,  in  regard  to  the  two 
species,  "The  specimens  from  the  different  islands  show  striking  though, 
in  most  cases,  slight  differences  distinguishing  the  individuals  of  each 
island  as  a  race,  from  those  inhabiting  any  other  island.  There  are 
two  exceptions.  Abingdon  and  Bindloe  have  the  same  form,  and  Albe- 
marle supports  at  least  two  races."  Each  of  these  two  species  presents 
no  less  than  five  racial  types,  to  which  distinctive  names  have  been 
applied.  Though  the  relationships  and  evolution  of  these  races  have 
been  ably  discussed  by  Snodgrass,  definite  conclusions  upon  these 
subjects  are  still  needed. 

Faiinal  Realms. — The  general  distribution  of  hfe  is  such  that 
naturalists  divide  the  earth  into  several  realms,  each  of  which  has  its 
characteristic  fauna  and  flora.  As  to  the  precise  boundaries  of  these 
faunal  realms,  zoologists  do  not  all  agree,  owing  chiefly  to  the  fact  that 


DISTRIBUTION  331 

faunfe  overlap  one  another  to  such  an  extent  as  to  render  their  exact 
separation  more  or  less  arbitrary.  Five  realms,  at  least,  are  generally 
recognized:  Holarctic,  Neotropical,  Ethiopian,  Oriental  and  Australian 
(Plate  III). 

The  Holarctic  realm  comprises  the  whole  of  Europe,  Northern 
Africa  as  far  south  as  the  Sahara,  Asia  down  to  the  Himalayas,  and 
North  America  down  to  Mexico.  Though  the  faunae  of  all  these  areas 
are  fundamentally  alike  (as  Merriam  and  other  authorities  maintain), 
it  is  often  convenient  to  divide  the  Holarctic  into  two  parts:  the 
Palcearctic,  including  Europe  and  most  of  temperate  Asia,  being  limited 
roughly  by  the  Tropic  of  Cancer;  and  the  Nearctic,  occupying  almost 
the  entire  continent  of  North  America,  including  Greenland.  The 
northern  portion  of  the  Holarctic  realm  forms  a  circumpolar  belt  with  a 
remarkably  homogeneous  fauna  and  flora;  therefore  some  authors 
distinguish  an  Arctic  realm,  limited  by  the  isotherm  of  32°,  which  marks 
very  closely  the  tree-limit. 

The  boreal  insects  of  Eurasia  and  North  America  are  strikingly 
alike.  Dr.  Hamilton  has  catalogued  almost  six  hundred  species  of 
beetles  as  being  holarctic  in  distribution;  five  hundred  of  these  are  com- 
mon to  Europe,  Asia  and  North  America,  and  the  remainder  are  known 
to  occur  in  North  America  and  also  in  Europe  or  Asia ;  one  hundred  are 
cosmopohtan  or  sub-cosmopoHtan,  to  be  sure,  but  fifty  of  these  are 
probably  holarctic  in  origin,  for  example — Dermestes  lardarius  (larder 
beetle)  and  Tenebrio  molitor  (meal-worm).  Of  butterflies,  out  of  some 
two  hundred  and  fifty  species  that  are  found  in  the  United  States  east 
of  the  Rocky  Mountains,  scarcely  more  than  a  dozen  occur  also  in  the 
old  world.  North  of  the  United  States,  however,  as  Scudder  finds,  no 
fewer  than  thirteen  genera  are  represented  in  the  old  world  by  the  same 
or  by  allied  species. 

The  Neotropical  realm  embraces  South  America,  Central  America, 
the  West  Indies  and  the  coasts  of  Mexico;  Mexico  being  for  the  most 
part  a  transition  tract  between  the  Neotropical  and  the  Nearctic.  The 
richest  butterfly  fauna  in  the  world  is  found  in  tropical  South  America. 
To  this  region  are  restricted,  almost  without  exception,  the  Euploeinae 
and  Lemoniinae  and  over  ninety-nine  per  cent,  of  the  Libytheinae;  here 
the  Heliconiida;  and  Papilionidse  attain  their  highest  development,  as 
do  also  the  Cerambycidae,  or  longicorn  beetles. 

The  Ethiopian  realm  consists  of  Africa  south  of  the  Sahara,  Southern 
Arabia  and  Madagascar;  though  some  prefer  to  regard  Madagascar  as 
a  distinct  realm,  the  Lemurian.     According  to  Wallace,  the  Ethiopian 


^3^ 


ENTOMOLOGY 


realm  has  seventy-five  peculiar  genera  of  Carabidae  and  is  marvelously 
rich  in  Cetoniidas  and  Lycaenidae. 

The  Oriental  realm  includes  India,  Ceylon,  Tropical  China,  and  the 
Western  Malay  Islands.  In  the  richness  of  its  insect  fauna,  this  realm 
vies  with  the  Neotropical.'  Danaidae  and  Papilionidae  are  abundant, 
while  the  genus  Morpho  is  represented  by  some  forty  species;  of  Cole- 
optera,  Buprestidae  are  important  andLucanidae  especially  so. 

The  Australian  realm  embodies  Austraha,  New  Zealand,  the  Eastern 
Malay  Islands  and  Polynesia.  Buprestidae  are  here  represented  by 
forty-seven  genera,  of  which  twenty  are  peculiar;  against  this  showing, 
the  Oriental  has  forty-one  genera  and  the  Neotropical  thirty-nine  (Wal- 
lace). Strong  affinities  are  said  to  exist  between  the  Australian  and 
Neotropical  insect  faunae. 

Life  Zones  of  North  America. — Merriam,  the  chief  authority  upon 
the  subject,  says:  "The  continent  of  North  America  may  be  divided. 


■^^ 

tSfS^ 

v^ 

^^ 

\^ 

/^^ 

Fig.  299. — Distribution  of  Erynnis  mani- 
toba,  a  butterfly  restricted  to  subarctic  and 
subalpine  regions. — After  Scudder. 


Fig.  300.— Distribution  in  the  United 
States  of  Eudamus  proteus,  primarily  a  trop- 
ical butterfly. — After  Scudder. 


according  to  the  distribution  of  its  animals  and  plants,  into  three 
primary  transcontinental  regions — Boreal,  Austral  and  Tropical." 
(Plate  IV). 

The  Boreal  region  covers  the  northern  part  of  the  continent  to  about 
the  northern  boundary  of  the  United  States  and  continues  southward 
along  the  higher  portions  of  the  mountain  ranges.  This  region  is 
divided  into  three  transcontinental  zones:  (i)  the  Arctic- Alpine,  lying 
above  the  limits  of  tree  growth,  in  latitude  or  altitude;  (2)  the  Hudso- 
nian,  comprising  the  northern  part  of  the  great  transcontinental  conifer- 
ous forest  and  the  upper  timbered  slopes  of  the  highest  mountains  of  the 
United  States  and  Mexico;  (3)  the  Canadian,  covering  theremainder  of 
the  Boreal  region.  The  butterfly  Erynnis  manitoha  (Fig.  299)  is  strictly 
boreal  in  distribution. 


Plate  IV. 


DISTRIBUTION  335 

The  Austral  region  "covers  the  whole  of  the  United  States  and 
Mexico,  except  the  Boreal  mountains  and  the  Tropical  lowlands."  It 
comprises  three  transcontinental  belts:  (i)  the  Transition  zone,  in 
which  the  Boreal  and  the  Austral  overlap;  (2)  the  Upper  Austral;  (3) 
the  Lower  Austral.  The  butterfly  Eudamus  proteus  (Fig.  300)  is  re- 
stricted, generally  speaking,  to  the  Tropical  region  and  the  warmer  and 
more  humid  portions  of  the  Austral. 

The  Tropical  region  covers  the  southern  extremity  of  Florida  and 
of  Lower  California,  most  of  Central  America  and  a  narrow  strip  along 
the  two  coasts  of  Mexico,  the  western  strip  extending  up  into  California 
and  Arizona. 

These  divisions  are  based  primarily  upon  the  distribution  of  mam- 
mals, birds  and  plants,  and  the  three  primary  divisions  serve  almost 
equally  well  for  insects  also.  In  regard  to  the  zones,  however,  not  so 
much  can  be  said^ — for  insects  are  to  a  high  degree  independent  of  minor 
differences  of  climate.     Many  instances   of   this  are   given   beyond. 

The  insect  fauna  of  the  United  States  is  upon  the  whole  a  hetero- 
geneous assemblage  of  species  derived  from  several  sources,  and  the 
foreign  element  of  this  fauna  we  shall  consider  at  some  length. 

Paths  of  Diffusion  in  North  America. — It  may  be  laid  down  as  a 
general  rule  that  every  species  tends  to  spread  in  all  directions  and  does 
so  spread  until  its  further  progress  is  prevented,  in  one  way  or  another. 
The  paths  along  which  a  species  spreads  are  determined,  then,  by  the 
absence  of  barriers.  The  diffusion  of  insects  in  our  own  country  has 
received  much  attention  from  entomologists,  especially  in  the  case  of 
such  insects  as  are  important  from  an  economic  standpoint.  The  ac- 
cessions to  our  insect  fauna  have  arrived  chiefly  from  Asia,  Central  and 
South  America,  and  Europe. 

Webster,  our  foremost  student  of  this  subject,  to  whom  the  author 
is  indebted  for  most  of  his  facts,  names  four  paths  along  which  insects 
have  made  their  way  into  the  United  States:  (i)  Northwest — Northern 
Asia  into  Alaska  and  thence  south  and  east;  (2)  Southwest — Central 
America  through  Mexico ;  (3)  Southeast— West  Indies  into  Florida ;  (4) 
Eastern — from  Europe,  commercially. 

Northwest.^ — The  northern  parts  of  Europe,  Asia  and  North  America 
have  in  common  very  many  identical  or  closely  allied  species,  whose 
distribution  is  accounted  for  if,  as  geologists  assure  us,  Asia  and  North 
America  were  once  connected,  at  a  time  when  a  subtropical  climate 
prevailed  within  the  Arctic  Circle;  in  fact,  the  distribution  is  scarcely 
explicable  upon  any  other  theory.     Curiously  enough,  the  trend  of 


33(> 


ENTOMOLOGY 


diffusion  seems  to  have  been  from  Asia  into  North  America  and  rarely 
the  reverse,  so  far  as  can  be  inferred. 

The  lady-beetle,  Coccinella  quinquenotata,  occurring  in  Siberia  and 
Alaska,  has  spread  to  Hudson  Bay,  Greenland,  Kansas,  Utah,  CaHfornia 
and  Mexico;  while  C.  sanguinea,  well  known  in  Europe  and  Asia,  ranges 
from  Alaska  to  Patagonia ;  and  Ceratomegilla  fuscilahris  from  Vancouver 
and  Canada  to  Chile.  About  six  hundred  species  of  beetles  are  holarctic 
in  distribution,  as  was  mentioned.  Some  of  them  inhabit  different 
climatal  regions  in  different  parts  of  their  range;  thus  Lina  lapponica  in 
the  Old  World  "occurs  only  in  the  high  north  and  on  high  mountain 
ranges,  whereas  in  North  America  it  extends  to  the  extreme  southern 
portion  of  the  country,"  being  widely  diffused  over  the  lowlands 
(Schwarz).  Similarly,  Silpha  lapponica  is  strictly  arctic  in  Europe,  but 
is  distributed  over  most  of  North  America  ;5i/^/m  opaca,  on  the  contrary, 
is  common  all  over  Europe,  but  is  strictly  arctic  in  North  America. 
Silpha  atrata,  common  throughout  Europe  and  western  Siberia,  was 
introduced  into  North  America,  but  failed  to  estabhsh  itself. 

Southwest. — Very  many  species  have  come  to  us  from  Central 
America  and  even  from  South  America.  South  America  appears  to  be 
the  home  of  the  genus  Halisidota,  according  to  Webster,  who  has  traced 
several  of  our  North  American  species  as  offshoots  of  South  American 
forms.  Many  of  our  species  may  be  traced  back  to  Yucatan.  H.  cinc- 
tipes  ranges  from  South  America  to  Texas  and  Florida;  H.  tessellaris 
has  spread  northward  from  Central  America  and  now  occurs  over  the 
middle  and  eastern  United  States,  while  a  form  closely  like  tessellaris 
ranges  from  Argentina  to  Costa  Rica;  H.  carycs  follows  tessellaris,  and 
appears  to  have  branched  in  Central  America,  giving  off  E.  agassizii, 
which  extends  northward  into  CaHfornia.  Similarly  in  the  case  of  the 
Colorado  potato  beetle  {Leptinotarsa  decemlineata)  and  its  relatives. 
According  to  Tower,  the  parent  form,  L.  undecimlineata,  seems  to  have 
arisen  in  the  northern  part  of  South  America,  to  have  migrated  north- 
ward and,  in  the  diversified  Mexican  region,  to  have  spHt  into  several 
racial  varieties.  The  parent  form  grades  into  L.  multilineata  of  the 
Mexican  table  lands,  which  in  ttirn,  in  the  northern  part  of  the  Mexican 
plateau,  passes  imperceptibly  into  L.  decemlineata,  which  last  species  has 
spread  northward  along  the  eastern  slope  of  the  western  highlands,  west 
of  the  arid  region.  In  the  lower  part  of  the  Mexican  region  the  parent 
form  may  be  traced  into  L.juncta,  which  has  spread  along  the  low  humid 
Gulf  Coast,  up  the  Mississippi  valley  to  southern  Illinois,  and  along  the 
Gulf  Coast  and  up  the  Atlantic  coast  to  Maryland,  Delaware  and  New 


DISTRIBUTION  337 

Jersey.  In  general,  the  mountains  of  Central  America  and  Mexico  and 
the  plateau  of  Mexico  have  been  barriers  to  the  northward  spread  of 
many  species,  which  have  reached  the  United  States  by  passing  to  the 
east  or  to  the  west  of  these  barriers,  in  the  former  case  skirting  the  Gulf 
of  Mexico  and  spreading  northward  along  the  Mississippi  valley  or  along 
the  Atlantic  coast,  in  the  latter  event  traveling  along  the  Pacific  coast 
to  California  and  other  Western  states.  Not  a  few  species,  however, 
have  made  their  way  from  the  Mexican  plateau  into  New  Mexico  and 
Arizona ;  this  is  true  of  many  Sphingidae.  The  butterfly  A  nosia  berenice 
ranges  from  South  America  into  New  Mexico,  Arizona  and  Colorado; 
while  many  of  the  Libytheidae  have  entered  Arizona  and  neighboring 
states  from  Mexico.  The  chrysomeHd  genus  Diabrotica  is  almost  ex- 
clusively confined  to  the  western  hemisphere  and  its  home  is  clearly  in 
South  America,  where  no  fewer  than  367  species  are  found.  About  100 
species  occur  in  Venezuela  and  Colombia,  "of  which  11  extend  into 
Guatemala,  8  into  Mexico,  and  i  into  the  United  States."  We  have  18 
species  of  Diabrotica,  almost  all  of  which  can  be  traced  back  to  Mexico, 
and  several  of  them — as  the  common  D.  longicornis — to  Central 
America.  "The  common  Dynastes  tityus  occurs  from  Brazil  through 
Central  America  and  Mexico,  and  in  the  United  States  from  Texas  to 
Illinois  and  east  to  southern  New  York  and  New  England."  Erebus 
odora  ranges  from  Ecuador  and  Brazil  to  Colorado,  Illinois,  Ohio,  New 
England  and  into  Canada,  though  it  is  not  known  to  breed  in  North 
America,  being  in  fact  a  rare  visitor  in  our  northern  states. 

Southeast. — Many  South  American  species  have  made  their  way 
into  southern  and  western  Florida  by  way  of  the  West  Indies,  while 
some  subtropical  species  have  reached  Florida  probably  by  following 
around  the  Gulf  coast.  The  semitropical  insect  fauna  of  southern  and 
southwestern  Florida,  including  about  300  specimens  of  Coleoptera, 
according  to  Schwarz,  is  entirely  of  West  Indian  and  Central  American 
origin,  the  species  having  been  introduced  with  their  food  plants,  chiefly 
by  the  Gulf  Stream,  but  also  by  flight,  as  in  the  case  of  Sphingidae. 
Ninety-five  species  of  Hemiptera  collected  in  extreme  southern  Florida 
by  Schwarz  and  studied  by  Uhler  are  distinctly  Central  American  and 
West  Indian  in  their  affinities.  Indeed  Uhler  is  inclined  to  beheve  that 
the  principal  portion  of  the  Hemiptera  of  the  United  States  has  been 
derived  from  the  region  of  Central  America  and  Mexico. 

Eastern.— On  the  Atlantic  coast  are  many  European  species  of 
insects  which  have  arrived  through  the  agency  of  man.  Most  of  them 
have  not  as  yet  passed  the  Appalachian  mountain  system,  but  some 


338  ENTOMOLOGY 

have  worked  their  way  inland.  Thus  the  common  cabbage  butterfly 
{Pieris  m/>«),  first  noticed  in  Quebec  about  i860,  was  found  in  the  north- 
ern parts  of  Maine,  New  Hampshire  and  Vermont  five  or  six  years  later, 
was  established  in  those  states  by  1867,  entered  New  York  in  1868  and 
then  Ohio.  Aphodius  fossor  followed  much  the  same  course  from  New 
York  into  northeastern  Ohio,  as  did  also  the  asparagus  beetle  {Crioceris 
asparagi),  the  clover  leaf  weevil  {Hyper a  punctata),  the  clover  root 
borer  {Hylastinus  obscurus)  and  other  species.  In  short,  as  Webster  has 
pointed  out.  New  York  offers  a  natural  gateway  through  which  species 
introduced  from  Europe  spread  westward,  passing  either  to  the  north 
or  to  the  south  of  Lake  Erie. 

Inland  Distribution. — Pieris  rapce,  the  spread  of  which  in  North 
America  has  been  thoroughly  traced  by  Scudder,  reached  northern  New 
York  in  1868  (as  above),  but  appears  to  have  been  independently  intro- 
duced into  New  Jersey  in  1868,  whence  it  reached  eastern  New  York 
again  in  1870;  it  was  seen  in  northeastern  Ohio  in  1873,  Chicago  1875, 
Iowa  1878,  Minnesota  1880,  Colorado  1886,  and  has  extended  as  far 
south  as  northern  Florida,  but  is  apparently  unable  to  make  its  way 
down  into  the  peninsula. 

The  asparagus  beetle,  Crioceris  asparagi,  another  native  of  Europe, 
became  conspicuous  in  Long  Island  in  1856,  spread  southward  to 
Virginia  and  westward  to  Ohio,  where  it  was  taken  in  1886;  it  is  fre- 
quent now  in  Illinois  and  Wisconsin  and  is  known  in  Colorado  and 
California.  This  insect,  as  Howard  observes,  flies  readily,  and  may 
be  introduced  commercially  in  the  egg  or  larval  stage  on  bunches  of 
asparagus. 

The  clover  leaf  weevil,  Hypera  punctata,  common  over  Europe  and 
most  of  Asia,  was  found  in  Canada  some  seventy  years  ago,  has  spread 
into  Mississippi,  Texas,  Utah  and  Idaho,  and  is  present  on  the  Pacific 
coast  also. 

The  lesser  clover  leaf  weevil,  Phytonomus  nigrirostris,  introduced 
from  Europe  into  the  United  States,  has  spread  steadily  westward  and 
has  now  reached  Illinois,  where  it  has  been  common  since  1919. 

Cryptorhynchus  lapathi,  a  beetle  destructive  to  willows  and  poplars, 
and  common  in  Europe,  Siberia  and  Japan,  was  found  in  New  Jersey  in 
1882  and  in  New  York  in  1896,  though  known  for  many  years  previously 
in  Massachusetts.  It  became  noticeable  in  Ohio  in  1901,  and  is  steadily 
extending  its  ravages,  being  known  now  in  Minnesota. 

From  Colorado  the  well-known  potato  beetle  {Leptinotarsa  decem- 
lineata)  has  worked  eastward  since  1840,  reaching  the  Atlantic  coast, 


DISTRIBUTION  339 

and  has  even  made  its  way  several  times  into  Great  Britain,  only  to 
be  stamped  out  with  commendable  energy.  The  box-elder  bug  {Lep- 
tocoris  trivittatus)  is  similarly  working  eastward,  having  now  reached 
Ohio.  Formerly  the  Rocky  Mountain  locust  periodically  migrated  east- 
ward, but  always  met  a  check  in  the  moist  valley  of  the  Mississippi. 

The  chinch  bug  {Blissus  leucopterus),  the  distribution  of  which  has 
been  traced  by  Webster,  has  spread  from  Central  America  and  Mexico 
northward  along  the  Gulf  coast  into  the  United  States,  following  three 
paths:  (i)  along  the  Atlantic  coast  to  Cape  Breton;  (2)  along  the 
]\Iississippi  valley  and  northward  into  Manitoba;  (3)  along  the  western 
coast  of  Central  America  and  Mexico  into  Cahfornia  and  other  Western 
states.  Everywhere  this  insect  has  found  wild  grasses  upon  which  to 
feed,  but  has  readily  forsaken  these  for  cultivated  grasses  upon 
occasion. 

Every  year  some  of  the  southern  butterflies  reach  the  Northern  states, 
where  they  die  without  finding  a  food  plant,  or  else  maintain  a  precari- 
ous existence.  Thus  Iphiclides  ajax  occasionally  reaches  Massachusetts 
as  a  visitor  and  a  visitor  only;  Lartias  philenor,  however,  finds  a  limited 
amount  of  food  in  the  cultivated  Aristolochia.  P.  thoas,  one  of  the  pests 
of  the  orange  tree  in  the  South,  is  highly  prized  as  a  rarity  by  New  Eng- 
land collectors  and  is  able  to  perpetuate  itself  in  the  Middle  States  on  the 
prickly  ash  (Xanthoxylum).  The  strong- winged  grasshopper,  Schisto- 
cerca  americand,  belonging  to  a  genus  the  center  of  whose  dispersion  is 
tropical ;  America,  ranges  freely  over  the  interior  of  North  x\merica, 
sometimes  in  great  swarms,  and  its  nymphs  are  able  to  survive  in 
moderate  numbers  in  the  southern  parts  of  Illinois,  Ohio  and  other 
states  of  as  high  latitude,  while  the  adults  occasionally  reach  Ontario, 
Canada. 

Many  species  are  now  so  widely  distributed  that  their  former  paths 
of  -diffusion  can  no  longer  be  ascertained.  The  army  worm  {Cirphis 
unipuncta),  feeding  on  grasses,  and  occurring  all  over  the  United  States 
south  of  Lat.  45°  23'  N.,  is  found  also  in  Central  America,  throughout 
South  America,  and  in  Europe,  Africa,  Japan,  China,  India,  etc.;  in 
short,  it  occurs  in  all  except  the  coldest  parts  of  the  earth,  and  where  it 
originated  no  one  knows. 

Determination  of  Centers  of  Dispersal. — In  accounting  for  the 
present  distribution  of  fife,  naturalists  employ  several  kinds  of  evidence. 
Adams  recognizes  ten  criteria,  aside  from  palaeontological  evidence,  for 
determining  centers  of  dispersal: 

I.  Location  of  greatest  dififerentiation  of  a  type. 


340  ENTOMOLOGY 

2.  Location  of  dominance  or  great  abundance  of  individuals. 

3.  Location  of  synthetic  or  closely  related  forms  (Allen). 

4.  Location  of  maximum  size  of  individuals  (Ridgway-AUen) . 

5.  Location  of  greatest  productiveness  and  its  relative  stability, 
in  crops  (Hyde). 

6.  Continuity  and  convergence  of  lines  of  dispersal. 

7.  Location  of  least  dependence  upon  a  restricted  habitat. 

8.  Continuity  and  directness  of  individual  variations  or  modifica- 
tions radiating  from  the  center  of  origin  along  the  highways  of  dispersal. 

9.  Direction  indicated  by  biogeographical  affinities. 

10.  Direction  indicated  by  the  annual  migration  routes,  in  birds 
(Palmen). 

2.  Geological 

Means  of  Fossilization. — Abundant  as  insects  are  at  present,  they 
are  comparatively  rare  as  fossils,  the  fossil  species  forming  but  one  per 
cent,  of  the  total  number  of  described  species  of  insects.  The  absence 
of  insect  remains  in  sedimentary  rocks  of  marine  origin  is  explained  by 
the  fact  that  almost  no  insects  inhabit  salt  water;  and  terrestrial  forms 
in  general  are  ill-adapted  for  fossihzation.  The  hosts  of  insects  that  die 
each  year  leave  remarkably  few  traces  in  the  soil,  owing  perhaps,  in 
great  measure,  to  the  dissolution  of  chitin  in  the  presence  of  moisture. 

Most  of  the  fossil  insects  that  are  known  have  been  found  in  vege- 
table accumulations  such  as  coal,  peat  and  lignite,  or  else  in  ancient 
fresh-water  basins,  where  the  insects  were  probably  drowned  and 
rapidly  imbedded.  At  present,  enormous  numbers  of  insects  are 
sometimes  cast  upon  the  shores  of  our  great  lakes — a  phenomenon  which 
helps  to  explain  the  profusion  of  fossil  forms  in  some  of  the  ancient 
lake  basins. 

Insects  in  rich  variety  have  been  preserved  in  amber,  the  fossilized 
resin  of  coniferous  trees.  This  substance,  as  it  exuded,  must  have  en- 
tangled and  enveloped  insect  visitors  just  as  it  does  at  present.  Many 
of  these  amber  insects  are  exquisitely  preserved,  as  if  sealed  in  glass. 
Copal,  a  transparent,  amber-like  resin  from  various  tropical  trees,  par- 
ticularly Leguminosae,  has  also  yielded  many  interesting  insects. 

Ill-adapted  as  insects  are  by  organization  and  habit  for  the  com- 
moner methods  of  fossilization,  the  number  of  fossil  species  already 
described  is  no  fewer  than  three  thousand. 

Localities  for  Fossil  Insects.^ — The  Devonian  of  New  Brunswick 
has  furnished  a  few  forms,  found  near  St.  John,  in  a  small  ledge  that 


DISTRIBUTION  34I 

outcrops  between  tide-marks;  these  forms,  though  few,  are  of  extraor- 
dinary interest,  as  will  be  seen. 

For  Carboniferous  species,  Commentry  in  France  is  a  noted  locality, 
through  the  admirable  researches  of  Brongniart,  who  described  from 
there  97  species  of  48  genera,  representing  12  families  or  higher  groups, 
10  of  which  are  regarded  as  extinct;  without  including  many  hundred 
specimens  of  cockroaches  which  he  found  but  did  not  study.  In  this 
country  many  species  have  been  found  in  the  coal  fields  of  Illinois, 
Nova  Scotia,  Rhode  Island,  Pennsylvania  and  Ohio. 

Many  fine  fossils  of  the  Jurassic  period  have  been  found  in  the  litho- 
graphic limestones  of  Bavaria;  143  species  from  the  Lias — four  fifths  of 
them  beetles — were  studied  by  Heer. 

The  Tertiary  period  has  furnished  the  majority  of  fossil  specimens. 
To  the  Oligocene  belong  the  amber  insects,  of  which  900  species  are 
known  from  Baltic  amber  alone,  and  to  the  same  epoch  are  ascribed  the 
deposits  of  Florissant  and  White  River  in  Colorado  and  of  Green  River, 
Wyoming.  These  localities — the  richest  in  the  world — have  been  made 
famous  by  the  monumental  works  of  Scudder.  At  Florissant  there  is  an 
extinct  lake,  in  the  bed  of  which,  entombed  in  shales  derived  from  vol- 
canic sand  and  ash,  the  remains  of  insects  are  found  in  astonishing  pro- 
fusion. For  Miocene  forms,  of  which  1,550  European  species  are 
known,  the  QEningen  beds  of  Bavaria  are  celebrated  as  having  furnished 
844  species,  described  by  the  illustrious  Heer. 

Pleistocene  species  are  supplied  by  the  peats  of  France  and  Europe, 
the  lignites  of  Bavaria,  and  the  interglacial  clays  of  Switzerland  and 
Ontario,  Canada. 

Silurian  and  Devonian. — The  oldest  fossil  insect  known  consists  of 
a  single  hemipterous  wing,  Protocimex,  from 
the  Lower  Silurian  of  Sweden.  Next  in  age 
comes  a  wing,  PalaoUaUina  (Fig.  301),  of 
doubtful  position,^  from  the  Middle  Silurian 
of  France.     Following  these  are  six  specimens  fig.  301.— Paiaobiattina 

of  as  many  remarkable  species  from  the  Devon-  gfotS'iAR?^'^^  size.-After 
ian  shales  of  New  Brunswick.     The  specimens, 

to  be  sure,  are  nothing  but  broken  wings,  yet  these  few  fragments, 
interpreted  by  Dr.  Scudder,  are  rich  in  meaning.  All  are  neuropteroid, 
but  they  cannot  be  classified  satisfactorily  with  recent  forms  on  account 
of  being  highly  synthetic  in  structure.     Thus  Platephemera  antiqua  (Fig. 

*  There  is  some  evidence,  it  should  be  said,  that  this  species  is  not  an  insect.     Handlirsch 
denies  also  that  Protocimex  is  an  insect. 


342 


ENTOMOLOGY 


302),  though  essentially  a  May  fly  of  gigantic  proportions  (spreading 
probably  135  mm.),  has  an  odonate  type  of  reticulation;  while  Xenoneura 
(Fig.  303)  combines  characters  which  are  now  distributed  among  Ephe- 
meridas,  Sialidas,  Rhaphidiidae,  Coniopterygidas,  and  other  families, 
besides  being  in  many  respects  unique.  These  Devonian  forms  attained 
huge  dimensions  as  compared  with  their  recent  representatives;  Gere- 
phemera,  for  example,  had  an  estimated  expanse  of  175  millimeters. 


Fig.  302. — Platephemera  antiqua,  natural  size. — After  Scudder. 


Fig.  303. — Xenoneura  antiquorum,  five  times  natural  size. — After  Scudder. 

Carboniferous. — The  Carboniferous  age,  with  its  luxuriant  vegeta- 
tion, is  marked  by  the  appearance  of  insects  in  great  number  and  variety, 
still  restricted,  however,  to  the  more  generaHzed  orders.  The  domi- 
nance of  cockroaches  in  the  Carboniferous  is  especially  noteworthy,  no 
fewer  than  200  Palaeozoic  species  being  known  from  Europe  and  North 
America.  These  ancient  roaches  (Fig.  304)  differed  from  their  modern 
descendants  in  the  similarity  of  the  two  pairs  of  wings,  which  were  alike 
in  form,  size,  transparency  and  general  neuration,  with  six  principal 
nervures  in  each  wing;  while  in  recent  cockroaches  the  front  wings  have 
become  tegmina,  with  certain  of  the  veins  always  blended  together, 
though  the  hind  wings  have  retained  their  primitive  characteristics  with 
a  few  modifications,  such  as  the  expansion  of  the  anal  area.  Carboni- 
ferous cockroaches  furthermore  exhibit  ovipositors,  straight,  slender, 
and  half  as  long  again  as  the  abdomen — organs  which  do  not  exist  in 
recent  species. 


DISTRffiUTION 


343 


Lithomantis  (Fig.  305),  a  remarkable  form  from  Scotland,  possessed 
in  addition  to  its  four  large  neuropteroid  wings,  a  pair  of  prothoracic 


Fig.  304. — Eloblatlina  ma-  Fig.  305. — Lithomantis  carbonarius,  showing  protho- 

zona,    a    Carboniferous    cock-       racic  appendages.    Two  thirds  natural  size. — After  WooD- 
roach    from    Illinois.      Twice       ward. 
natural  size. — After  Scudder 
in  Miall  and  Denny. 


Fig.  306. — Stenodictya  lobata,  showing  wing-like  appendages  of  prothorax  and  abdomen. 
Natural  size. — After  Handlirsch. 


wing-like  appendages  which,  provided  they  may  be  regarded  as  homolo- 
gous with  wings,  represent  a  third  pair,  either  atrophied  or  undeveloped 


344  ENTOMOLOGY 

— a  condition  which  is  never  found  today,  unless  the  patagia  of  Lepidop- 
tera  represent  wings,  which  is  unhkely. 

Stenodidya  lohata  (Fig.  306)  described  by  Brongniart  from  the 
Upper  Carboniferous  of  Commentry,  France,  also  bears  prothoracic 
"wings"  and,  in  addition,  eight  pairs  of  abdominal  wing-like  or  gill-like 
appendages.  No  fewer  than  five  families  of  Palaeozoic  insects  are 
represented  by  specimens  having  prothoracic  wings. 

From  the  rich  deposits  of  Commentry,  Brongniart  has  described 
several  forms  of  striking  interest.     Dictyoneura  is  a  Carboniferous  genus 


Fig.  307. — Eugereon  bockingi.     Three  quarters  natural  size. — After  Dohrn. 

with  neuropteroid  wings  and  an  orthopteroid  body,  having,  in  common 
with  several  contemporary  genera,  strong  isopteran  affinities.  Coryda- 
loides  scudderi,  a  phasmid,  has  an  alar  expanse  of  twenty-eight  inches. 
The  Carboniferous  prototypes  of  our  Odonata  were  gigantic  beside  their 
modern  descendants,  one  of  them  {Meganeura)  having  a  spread  of  more 
than  two  feet;  they  were  more  generalized  in  structure  than  recent 
Odonata,  presenting  a  much  simpler  type  of  neuration  and  less  differen- 
tiation of  the  segments  of  the  thorax.  The  Carboniferous  precursors  of 
our  May  flies  attained  a  high  development  in  number  and  variety;  in 
fact,  the  Ephemeridae,  like  the  Blattidae,  achieved  their  maximum 
development  ages  ago,  when  they  attained  an  importance  strongly  con- 
trasting with  their  present  meager  representation. 

The  Permian  has  supplied  a  remarkable  genus  Eugereon  (Fig.  307) 


DISTRIBUTION  345 

with  hemipterous  mouth  parts  associated  with  filiform  antennaj  and 
orthopteroid  wings.  The  earliest  unquestionable  traces  of  insects  with 
an  indirect  metamorphosis  are  found  in  the  Permian  of  Bohemia,  in 
the  shape  of  caddis-worm  cases. 

Triassic. — Triassic  cockroaches  present  interesting  stages  in  the 
evolution  of  their  family.  Through  these  Mesozoic  species  the  con- 
tinuity between  Palaeozoic  and  recent  cockroaches  is  clearly  established 
— which  can  be  said  of  no  other  insects;  and  in  fact  of  no  other  animals, 
the  only  comparable  cases  being  those  of  the  horse  and  the  moUuscan 
genus  Planorhis.  In  the  Triassic  period  occur  the  first  fossils  that  can  be 
referred  indisputably  to  Coleoptera  and  Hymenoptera,  the  latter  order 
being  represented  first,  as  it  happens,  by  some  of  its  most  specialized 
members,  namely  ants. 

Jurassic. — At  length,  in  the  Jurassic,  all  the  large  orders  except  Lep- 
idoptera  occur;  Diptera  appear  for  the  first  time,  and  Odonata  are  rep- 
resented by  many  well-preserved  specimens,  while  the  Liassic 
Coleoptera  studied  by  Heer  number  over  one  hundred  species.  The 
Cretaceous  has  yielded  but  few  insects,  as  might  be  expected. 

Tertiary. — In  the  rich  Tertiary  deposits  all  orders  of  insects  occur. 
Baltic  amber  has  yielded  Collembola,  some  remarkable  Psocidae,  many 
Diptera,  and  ants  in  abundance.  Of  844  species  taken  from  the  noted 
Miocene  beds  of  OEningen,  nearly  one  half  were  Coleoptera,  followed  by 
neuropteroid  forms  (seventeen  per  cent.)  and  Hymenoptera  (fourteen 
per  cent.) ;  ants  were  twice  as  numerous  in  species  as  they  are  at  present . 
in  Europe.  Almost  half  the  known  species  of  fossil  insects  have  been 
described  from  the  Miocene  of  Europe.  To  the  Miocene  belongs  -the 
indusial  limestone  of  Auvergne,  France,  where  extensive  beds — in  some 
places  two  or  three  meters  deep — consist  for  the  most  part  of  the  cal- 
cified larval  cases  of  caddis  flies. 

At  Florissant,  as  contrasted  with  Q^ningenby  Scudder,  Hymenoptera 
constitute  4.0  per  cent,  of  the  specimens,  owing  chiefly  to  the  predomi- 
nance of  ants;  Diptera  follow  with  30  per  cent,  and  then  Coleoptera  with 
13  per  cent.  Modern  famihes  are  represented  in  great  profusion.  The 
material  from  Florissant  and  neighboring  locahties  includes  a  Lepisma, 
fifteen  species  of  Psocidae,  more  than  thirty  species  of  Aphididae,  and 
more  than  one  hundred  species  of  Elateridae,  while  the  Rhynchophora 
number  193  species  as  against  150  species  from  the  Tertiary  of  Europe. 
Tipulidae  are  abundant  and  exquisitely  preserved,  while  Bibionidae,  as 
compared  with  their  present  numbers,  are  surprisingly  common.  Nu- 
merous masses  of  eggs  occur,  undoubtedly  sialid  and  closely  like  those  of 


346  ENTOMOLOGY 

Corydalis.  Sialid  characters,  indeed,  appear  in  the  oldest  fossils  known, 
and  are  strongly  manifest  throughout  the  fossil  series,  though  among 
recent  insects  Sialidae  occupy  only  a  subordinate  place.  Strange  to  say, 
few  aquatic  insects  have  been  found  in  this  ancient  lake  basin. 

Fossil  butterflies  are  among  the  greatest  rarities,  only  seventeen 

being  known;  yet  Florissant  has 
contributed  eight  of  these,  a  few  of 
which  are  marvelously  well  pre- 
served (Fig.  308),  as  appears  from 
Scudder's  figures.  Two  of  the 
Florissant  specimens  belong  to 
Libytheinae,  a  group  now  scantily 
represented,  though  widely  distri- 
buted over  the  earth.  The  group 
is  structurally  an  archaic  one,  and 
Fig.  308. — Prodryas  persephone,  a  fossil     its  recent   members  (forming  only 

butterfly  from  Colorado.     Natural  size. —  •1.1  1       i.i       r  .-i       •,  m      i 

After  ScuDDER.  One  eight-hundredth  of  the  described 

species  of  butterflies)  are  doubtless 
relicts. 

Taken  as  a  whole,  the  insect  facies  of  Tertiary  times  was  apparently 
much  the  same  as  at  present.  The  Florissant  fauna  and  flora  indicate, 
however,  a  former  climate  in  Colorado  as  warm  as  the  present  climate 
of  Georgia. 

Quaternary. — The  interglacial  clays  of  Toronto,  Ontario,  have  yielded 
fragments  of  the  skeletons  of  beetles  to  the  extent  of  several  hundred 
specimens,  about  one  third  of  which  (chiefly  elytra)  were  sufficiently 
complete  or  characteristic  to  be  identified  by  Dr.  Scudder,  who  found  in 
all  76  species  of  beetles,  representing  8  families,  chiefly  Carabidae  and 
Staphylinidae.  All  these  interglacial  beetles  are  referable  to  recent 
genera,  but  none  of  them  to  recent  species,  though  the  differences 
between  the  interglacial  species  and  their  recent  alHes  are  very  slight. 
As  a  whole,  these  species  "indicate  a  climate  closely  resembling  that  of 

Ontario  to-day,  or  perhaps  a  sHghtly  colder  one One  cannot 

fail,  also,  to  notice  that  a  large  number  of  the  allies  of  the  interglacial 
forms  are  recorded  from  the  Pacific  coast."  (Scudder.)  The  writer, 
who  has  studied  these  specimens,  has  been  impressed  most  by  their 
Hkeness  to  modern  species.  It  is  indeed  remarkable  that  so  little 
specific  differentiation  has  occurred  in  these  beetles  since  the  inter- 
glacial epoch — certainly  ten  thousand  and  possibly  two  to  three  hundred 
thousand  years  ago. 


DISTRIBUTION  347 

General  Conclusions. — Unfortunately,  the  earliest  fossils  with 
which  we  are  acquainted  shed  much  less  light  upon  the  subject  of  insect 
phylogeny  than  one  might  expect.  The  few  Devonian  forms,  though 
synthetic  indeed  as  compared  with  their  modern  allies,  are  at  the  same 
time  highly  organized,  or  far  from  primitive,  and  their  ancestors  have 
been  obliterated. 

The  general  plan  of  wing  structure,  as  Scudder  finds,  has  remained 
unaltered  from  the  earliest  times,  though  the  Devonian  specimens 
exhibit  many  peculiarities  of  venation,  in  which  respect  some  of  them  are 
more  specialized  than  their  nearest  living  allies,  while  none  of  them 
have  much  special  relation  to  Carboniferous  forms. 

Carboniferous  insects  are  more  nearly  related  to  recent  forms  than  are 
the  Devonian  species,  but  present  a  number  of  significant  generalized 
features.  Generally  speaking,  the  thoracic  segments  were  similar  and 
unconsolidated,  and  the  two  pairs  of  diaphanous  wings  were  alike  in 
every  respect — in  groups  that  have  since  developed  tegmina  and  dis- 
similar thoracic  segments.  The  Carboniferous  precursors  of  our  cock- 
roaches, phasmids  and  May  flies  have  been  mentioned.  Palasozoic 
insects  were  grouped  by  Scudder  into  a  single  order,  Palaeodictyoptera,  on 
account  of  their  synthetic  organization,  though  other  authors  have  tried 
to  distribute  them  among  the  modern  orders.  This  disagreement  will 
continue  until,  with  increasing  knowledge,  our  classification  becomes 
less  arbitrary  and  more  natural. 

Mesozoic  insects  are  interesting  chiefly  as  evolutionary  links, 
notably  so  in  the  case  of  cockroaches — the  only  insects  whose  ancestry 
is  continuously  traceable.  In  this  era  the  large  families  became  differen- 
tiated out. 

Most  of  the  Tertiary  species  are  referable  to  recent  genera,  peculiar 
famihes  being  highly  exceptional,  while  all  the  Quaternary  species 
belong  to  recent  genera. 

Hemiptera  appear  in  the  Silurian;  Neuroptera  (in  the  old  sense)  in 
the  Devonian;  Thysanura  and  Orthoptera,  Carboniferous;  Coleoptera 
and  Hymenoptera,  Triassic;  Diptera,  Jurassic;  and  Lepidoptera  not 
until  the  Tertiary. 

Since  Scudder's  day,  considerable  additions  to  the  knowledge  of  our 
fossfl  insects  have  been  made  by  Professor  T.  D.  A.  Cockerell  and 
by  Professor  H.  F.  Wickham. 

A  comprehensive  and  richly  illustrated  account  of  fossil  insects  is 
given  by  Handlirsch  in  his  great  work.  Die  fossilen  Insekten. 


CHAPTER  XIII 

INSECT  ECOLOGY 

Ecology  is  the  physiology  of  organisms  in  relation  to  environment. 
It  is  the  physiology  of  entire  organisms  rather  than  of  organs.  It  deals 
with,  the  reactions  of  organisms  to  the  conditions  of  their  existence, 
including  the  modification  of  these  reactions  in  relation  to  changes  of 
environment. 

Though  its  subject  matter  is  primarily  animals  and  plants,  ecology 
is  based  upon  all  the  sciences,  and  cannot  be  pursued  most  precisely 
without  the  aid  of  some  mathematics. 

Insect  life  in  its  omnipresence  and  diversity  affords  countless  illus- 
trations of  ecological  principles,  under  which  innumerable  isolated 
observations  fall  into  organization. 

The  qualitative  study  of  the  subject  is  simply  a  matter  of  accurate 
and  thorough  observation  and  correct  inference,  with  the  aid  of  the 
simplest  kind  of  experimentation.  Even  in  quantitative  investigation, 
the  ecological  principles  may  be  brought  out  with  the  use  of  such 
inexpensive  means  as  thermometers,  ice-boxes,  weather  maps,  etc. 
For  the  most  refined  work,  however,  elaborate  appliances  for  controlling 
ecological  factors  are  often  necessary. 

It  should  be  remembered  that  the  study  of  insects  alone  gives  only 
a  partial  understanding  of  ecology,  with  an  imperfect  perspective  of 
the  subject. 

The  ecology  of  individuals  is  known  as  Autecology;  that  of  com- 
munities, as  Synecology. 

I.  Conditions  of  Terrestrial  Existence 
I.  Soil 

The  edaphic  conditions  of  existence  (those  relating  to  the  soil)  are 
the  same  for  animals  and  plants,  but  are  utiHzed  in  different  ways  by 
these  organisms.  Plants  can  utilize  inorganic  constituents  of  the  soil 
as  food,  but  animals  can  not.  All  the  food  of  animals,  with  such 
exceptions  as  water  and  salt,  is  derived  in  the  last  analysis  from  plants. 

Structure. — The  retention  of  water  by  the  soil  depends  largely  upon 
the  size  of  the  soil  particles;  soil  of  small  particles  holding  more  water 

348 


INSECT   FXOLOGY  349 

than  one  of  large  particles.  Water  evaporates  more  rapidly  from 
coarse  soils  than  from  fine  ones,  but  in  loose  soils  the  more  rapid  evapora- 
tion from  the  surface  forms  an  aerated  "mulch"  which  retards  further 
evaporation.  The  different  capacities  of  different  soils  for  absorbing 
or  retaining  moisture  affects  insects  indirectly  by  its  effects  on  vegetation, 
or  may  affect  them  directly.  The  compactness  of  loose  soils  varies  with 
the  amount  of  water  present,  which  is  of  importance  to  burrowing  insects. 
A  good  example  of  this  is  seen  in  the  sandy  beach  of  a  lake,  when  the 
sand  wet  by  waves  becomes  firm;  the  water  evaporates  rapidly,  however, 
until  the  sand  is  dry  again,  in  proportion  to  its  nearness  to  the  surface. 
In  such  sand,  with  frequent  alternations  from  wet  to  dry,  insects  do  not 
live;  though  some  forms,  as  tiger  beetles  and  beetles  of  the  genus 
Bembidion,  burrow  in  the  sand  a  little  farther  back  from  the  shore, 
where  the  fluctuations  in  the  water  content  are  not  so  great. 

In  a  loose  soil  white  grubs  or  wireworms  go  easily  and  rapidly  from 
one  plant  to  another.  Tiger  beetles  and  ants  need  soil  of  a  consistence 
which  will  maintain  the  burrows  after  they  are  made.  Caterpillars, 
grubs,  etc.,  about  to  pupate,  can  not  burrow  in  soil  that  is  too  hard,  and 
frequently  avoid  also  soil  that  is  too  loose.  The  bollworm  if  unable  to 
dig  into  hard  baked  soil  will  enter  cracks  in  the  soil.  Some  grasshoppers, 
on  the  other  hand,  prefer  hard-packed  soil  in  which  to  lay  their  eggs. 
In  making  their  pupal  cells  in  the  ground,  larvae  press  the  surrounding 
soil  into  a  compact  wall,  often  adding  a  cementing  fluid  which  is  fre- 
quently waterproof.  The  bollworm,  or  corn  ear  worm,  lines  its  burrow 
with  silk. 

A  soil  of  loose  texture  faciHtates  the  emergence  of  adult  insects. 
If  the  soil  is  too  hard  they  may  not  be  able  to  emerge  until  it  has  been 
softened  by  rain.  Plowing  and  roUing  the  soil  of  a  stubble  field  in 
summer  is  known  to  prevent  the  exit  of  Hessian  flies. 

The  depth  to  which  insects  burrow  in  the  ground  depends  upon  the 
physical  nature  of  the  soil,  and  temperature  and  moisture  as  well. 

Chemical  Conditions. — In  addition  to  oxygen,  carbon  dioxide 
and  nitrogen,  the  soil  contains  other  gases  and  various  chemical  com- 
pounds, some  of  which  are  essential  to  plant  life  and  therefore  indirectly 
to  the  welfare  of  animals.  The  character  of  the  vegetation  as  determined 
by  the  acidity  or  alkalinity  of  the  soil  affects  the  character  of  the  insect 
fauna.  The  acid  water  of  bogs  is  directly  unfavorable  to  insect  life, 
but  is  favorable  to  the  growth  of  peculiar  plants  which  are  selected  as 
food  by  certain  insects.  In  New  Jersey,  Mr.  H.  Bird,  by  acidulating 
soil  with  an  artificial  bog  water  made  with  the  extract  of  hemlock  used 


350  ENTOMOLOGY 

for  tanning  leather,  succeeded  in  growing  the  pitcher  plant,  Sarracenia 
purpurea,  and  in  raising  thereon  a  species  of  rare  moth,  Papaipema 
appassionata,  known  for  thirty  years  only  by  a  unique  type  in  the 
British  Museum. 

Plants  of  alkaline  desert  soils  have  their  characteristic  insect  fauna. 

Air.- — The  oxygen  content  of  subterranean  air  is  important  directly 
for  respiration;  indirectly  for  its  effects  on  vegetation.  Aeration  of  the 
soil  is  essential  to  subterranean  life.  In  too  compact  a  soil  insects 
suffer  from  lack  of  oxygen  and  excess  of  carbon  dioxide,  and  may 
experience  also  the  effects  of  excessive  evaporation  and  mechanical 
difficulties  in  burrowing. 

Water. — For  their  welfare,  soil  insects  must  have  neither  too  much 
nor  too  httle  water.  They  may  be  drowned  by  gravitational  water, 
which  acts  also  by  fiUing  the  air  spaces  around  soil  particles.  Sub- 
mersion was  used  effectively  in  France  against  the  destructive  Phyl- 
loxera of  the  grape.  Capillary  water  is,  on  the  contrary,  favorable  to 
the  insect  life  until  it  evaporates  to  excess.  As  with  terrestrial  insects, 
the  vital  effects  of  water  and  temperature  are  produced  through 
evaporation,  in  relation  to  which  soil  forms  exhibit  various  adaptations. 
As  the  soil  dries,  ants  dig  deeper.  The  depth  of  pupal  chambers, 
their  compact  waterproofed  walls,  and  the  air  space  around  the  pupa, 
and  the  closing  of  the  entrance  to  the  burrow,  all  tend  to  protect  the 
pupa  from  undue  loss  of  bodily  moisture. 

With  the  tiger  beetles,  the  amount  of  moisture  determines  whether 
eggs  are  to  be  laid,  and  their  number  if  laid;  eggs  being  absent  in  dry 
soil  (Shelford). 

Temperature.— There  are  great  differences  in  the  temperatures  of 
different  soils,  from  dry  sands  to  moist  shaded  humus.  Temperature 
and  moisture  determine  largely  the  character  of  the  flora  and  of  the 
accompanying  fauna.  The  greater  the  depth  of  soil  the  lower  the  tem- 
perature as  a  rule.  Ants  and  other  insects  will  dig  deeper  to  avoid  heat 
as  well  as  dryness.  Ants  often  find  suitable  conditions  of  temperature 
and  moisture  under  stones  or  logs. 

In  the  case  of  insects  that  are  said  to  be  killed  by  heat,  the  mortality 
is  due  primarily  to  evaporation  and  secondarily  to  the  coagulation  of  the 
protoplasm;  perhaps  also  to  ultra-violet  rays. 

Physiographic  Conditions. — As  environmental  factors  there  must 
be  considered  also  the  nature  of  the  surface  of  the  soil  as  regards  exposure 
or  cover,  the  slope  of  the  soil,  and  the  altitude  at  which  it  is  found. 
All  these  things  affect  the  fauna.     Angle  of  slope  has  an  effect  in 


INSECT    ECOLOGY  35 I 

determining  the  presence  or  absence  of  oviposition  burrows  of  tiger 
beetles,  and  the  presence,  absence,  or  number  of  eggs  laid  (Shelf ord). 

Nutriment. — The  food  of  soil  insects  may  be  roots  or  stems  of 
plants,  dead  animal  or  vegetable  matter,  other  insects  or  other  animals. 
Some  insects  are  parasitic  on  burrowing  mammals.  Many  ants  derive 
part  of  their  nourishment  from  the  root-sucking  aphids  or  coccids 
which  they  attend.  Ants  and  termites  sustain  diverse  relations  as 
regards  food  with  various  other  insects  and  other  arthropods  that  live 
in  their  nests.  Some  species  that  burrow  near  the  surface,  as  tiger 
beetles  and  ant-lions,  capture  their  prey  from  the  surface  of  the  ground. 

Soil  that  contains  no  organic  matter,  as  pure  quartz  sand,  is  food 
for  no  insect.  Some  larvae,  as  white  grubs  and  wireworms,  that  subsist 
primarily  on  roots  of  plants,  can  if  necessary  thrive  for  many  months  on 
a  diet  of  soil  alone,  but  only  because  of  the  organic  matter  that  it 
contains. 

Interactions. — The  subject  of  interactions  in  the  soil  environment 
can  only  be  touched  upon  here.  The  character  of  the  soil  itself  is 
changed  by  the  plants  and  animals  that  inhabit  it.  Thus  burrowing 
animals,  as  worms,  crawfishes,  insects,  moles,  mice,  many  larger 
mammals,  etc.,  alter  the  distribution  and  the  physical  and  chemical 
composition  of  the  soil.  Bacteria  and  fungi  play  important  parts. 
The  soil  is  not  fully  effective  in  protecting  its  insect  inhabitants  from 
predaceous  and  parasitic  enemies  among  other  insects,  and  soil  insects 
are  themselves  food  for  many  birds,  mammals,  and  other  of  the  larger 
animals. 

2.  Atmosphere 


The  most  conspicuous  effect  of  hght  is  its  directive  effect  on  locomo- 
tion. This  phenomenon  is  discussed  in  another  chapter  (p.  306), 
where  it  is  shown  that  insects  react  either  positively  or  negatively  to 
light,  are  often  attuned  to  definite  ranges  of  light  intensity,  and  react 
differently  to  hght  of  different  wave  lengths.  The  results  of  photo- 
tropism  are  often  incidentally  adaptive.  As  examples,  the  positive 
reaction  may  take  insects  to  their  food,  cause  the  nuptial  flight  of  ants 
or  termites,  or  the  swarming  of  bees;  while  the  negative  response  may 
lead  insects  into  places  of  concealment,  pupation,  or  hibernation. 
Structures  and  functions  are  correlated  with  the  presence  or  the  absence 
of  light;  for  example,  those  of  the  eyes.  Insects  that  Kve  in  darkness, 
as  boring  species,  subterranean  forms,  and  cave  insects,  exhibit  special 


352  ENTOMOLOGY 

modifications  in  relation  to  the  absence  of  light  that  are  mentioned  in 
other  parts  of  this  book. 

Growth.- — In  nature  the  effects  of  light  on  growth  are  bound  up 
with  those  of  temperature.  The  temperature  of  the  air  varies  with 
light  {insolation,  or  exposure  to  the  sun's  rays) .  Cloudy  summer  days 
are  cooler  than  sunny  days.  Cloudy  winter  days  are  warmer.  (Shel- 
ford.)  Light  affects  the  rate  of  growth,  or  more  precisely,  some  wave 
lengths  are  more  effective  than  others.  Beclard  reared  larvae  of  the 
flesh-fly,  Musca  carnivora,  from  the  eggs,  under  glass  bells  of  different 
colors.  The  largest  larvae  were  found  under  violet  or  blue;  the  smallest 
under  green;  the  colors  producing  their  effects  in  the  following  order: 
violet,  blue,  red,  yellow,  white,  green.  Under  violet  the  larvas  were 
three-quarters  greater  than  under  green.  Green  rays  retarded  growth, 
as  did  also  white  light.     (C.  B.  Davenport.) 

Activity. — Sunshine,  aside  from  temperatures,  unless  they  are 
extreme,  has  a  stimulating  effect  on  reproduction  and  other  activities 
in  flies  (Bishopp,  Dove,  Parman) ;  and  this  is  true  probably  for  most 
diurnal  insects.  On  cloudy  days  the  boll  weevil  and  most  other 
insects  as  well  are  less  active  than  on  clear  days,  without  regard  to 
temperature. 

Exposure  to  hot  sunshine  kills  pupae  of  the  bollworm,  plum  curculio 
and  other  forms.  This  result  is  due  primarily  to  heat  with  evaporation, 
but  possibly  the  ultra-violet  rays  also  exert  some  influence. 

Sleep.- — Whatever  the  temperature  may  be,  insects  go  to  sleep  when 
■  night  falls,  and  do  so  during  the  daytime  if  clouds  diminish  the  sunlight 
beyond  a  certain  point  which  varies  for  different  species.  If  it  becomes 
very  cloudy,  the  mourning-cloak,  Vanessa  antiopa,  seeks  some  crevice 
and  goes  to  sleep,  but  is  quickly  aroused,  however,  by  returning  sun- 
shine. The  sleep  of  insects  doubtless  has  the  same  physiological 
results  as  that  of  other  animals. 

"A  few  species  seem  to  choose  protectively  colored  situations,  and 
others  select  sites  which  are  in  various  ways  protective.  Some  which 
are  solitary  by  day  are  gregarious  at  night,  and  some  insects  sleep  with 
all  the  regularity  of  a  theoretical  modern  infant,  while  others  of  a  more 
unsystematic  life  snatch  a  wink  when  they  can. "     (P.  Rau  and  N.  Rau.) 

Temperature 

Temperature  Limits. — It  goes  without  saying  that  the  life-processes 
and  the  activities  of  every  animal  or  plant  are  confined  within  a  certain 
range   of   temperature,    outside   of  which  the  organism  cannot  exist. 


INSECT  ECOLOGY  353 

This  range  is  different  for  different  species,  for  the  same  species  in  differ- 
ent seasons  or  places,  and  is  different  even  for  different  individuals  of 
the  same  species  under  apparently  equal  conditions,  and  for  different 
stages  in  the  growth  or  development  of  the  same  individual.  The 
temperature-range  is  affected  by  food,  moisture,  evaporation,  and 
several  other  factors. 

Growth  and  development  proceed  most  rapidly  in  a  certain  optimum 
range  of  temperature,  within  which  there  is,  at  least  theoretically,  an 
optimum  degree  of  temperature.  At  and  above  a  certain  degree  of 
high  temperature  heat-rigor  sets  in,  and  may  or  may  not  be  fatal  to  an 
organism,  according  to  the  duration  of  the  exposure  to  the  temperature. 
This  maximimi  temperature  has  as  its  upper  limit  the  uUramaximum, 
at  which  the  organism  dies  at  once,  probably  because  of  the  coagulation 
of  proteids  in  the  protoplasm.  At  a  certain  degree  of  low  temperature, 
cold-rigor  takes  place;  the  point  at  which  it  occurs  being  near  the  freez- 
ing point,  on  account  of  the  fluid  content  of  protoplasm.  Below  this 
minimum  is  an  ultraminimum  temperature,  at  which  the  organism  dies. 

The  following  examples  of  temperature-limits  are  from  Davenport's 
Experimental  Morphology. 

Insect  Maximum  Ultramaximum 

Springtail,  Podiira  similata 27°  C.  36.0°  C, 

Mosquito,  Culex  pipiens 40°  C.  

Larva  of  fly,  Musca  vomitoria , 42 . 5°  C. 

Pupa  of  fly,  Musca  vomitoria 43 . 7°  C. 

Silkworm,  Bombyx  mori 42 . 5°  C. 

Back-swimmer,  Notoneda 45 . 0°  C. 

It  should  be  noted  that  the  Podura  (near  Achorutes)  has  a  thin 
integument,  and  can  not  live  in  a  dry  atmosphere.  The  pupa  of  the 
fly  is  protected  somewhat  by  its  puparium,  and  the  back-swimmer  by 
a  fairly  thick  integument. 

Insect  Ultraminimum 

Honey  bee,  Apis  mellifera —   i .  5°  C. 

House  fly,  Musca  domestica —  5 . 0°  C. 

Larva  of  cockchafer,  Melolontha — 15 .0°  C. 

Adult  cockchafer,  Melolontha — 18 . 0°  C. 

Davenport  notes  that  the  large  size  and  thick  covering  of  the  beetle, 
Melolontha  prevent  the  rapid  loss  of  heat. 

Activity  in  Relation  to  Temperature. — The  range  of  activity  of  the 
adult  cotton  boll  weevil  lies  between  56°  F.  and  95°  F.  From  95°  to 
122°  is  the  range  of  aestivation,  within  which  the  beetles  are  inactive. 
From  122°  to  140°  (soil  temperature)  is  an  upper  range  of  fatal  tem- 

23 


354  ENTOMOLOGY 

peratures,  in  which  the  weevil  dies  in  15  minutes  to  i  second,  according 
to  the  temperature,  140°  being  the  maximum  fatal  temperature. 

In  the  descending  scale  of  temperature,  there  is  a  range  between  56° 
to  24°  within  which  the  beetles  hibernate.  Below  24°  is  the  lower  range 
of  fatal  temperatures,  with  7°  as  the  minimum  fatal  temperature.  As 
the  hmits  of  these  ranges  vary  with  moisture  and  other  factors,  these 
ranges,  as  given  by  Hunter  and  Pierce  (191 2)  are  necessarily  approxima- 
tions; but  they  serve  to  illustrate  the  fact  that  such  ranges  exist,  and 
are  accurate  for  the  particular  conditions  under  which  they  were  made. 

It  may  be  mentioned  that  Hunter  and  Pierce  found  that  the  winter 
cold  is,  on  the  average,  almost  twice  as  effective  as  summer  heat  in 
kilhng  the  beetle;  which  has  several  times  been  greatly  reduced  in 
numbers  by  early  freezes  in  the  South. 

High  temperatures  are  more  favorable  to  the  activities  of  insects 
than  to  those  of  human  beings.  The  temperature  range  of  activity 
varies  with  different  species. 

The  effect  of  temperature  upon  the  locomotor  activity  of  the  boll 
weevil  was  tested  by  Dr.  A.  W.  Morrill,  who  found  that  as  the  tem- 
perature was  gradually  raised  the  activity  of  the  weevils  increased  up 
to  105°  F.  At  95°  the  beetles  were  very  active;  at  86°  they  began  to 
lose  their  activity;  and  at  37°  all  movement  ceased.  Out  of  doors, 
weevil  activity  began  and  ceased  at  about  75°;  feeding  continuing  at 
lower  temperatures  than  oviposition. 

The  number  of  daily  feeding  punctures  of  the  weevil  was  found  to  be 
greatest  at  about  80°  F.,  as  was  also  the  number  of  eggs  laid.  (Hunter 
and  Hinds.) 

The  curve  representing  the  average  number  of  eggs  deposited  daily 
by  the  alfalfa  weevil,  Phytonomus  posticus,  follows  the  curve  of  the  mean 
daily  temperature  in  all  its  major  fluctuations,  the  highest  record 
(twenty-six  eggs)  occurring  on  the  day  (May  18)  with  the  highest  mean 
temperature  (72°  F.)  of  any  day  previous  to  June  6.     (T.  H.  Parks.) 

By  stimulating  the  activities  of  insects,  high  temperatures  diminish 
the  longevity.  Thus  a  worker  honey  bee  that  hibernates  may  live  for 
six  or  seven  months,  but  an  active  worker  in  summer  lives  only  five  or 
six  weeks. 

Other  things  being  equal,  the  longevity  of  insects  in  general  is 
lengthened  by  a  decrease  in  temperature  and  shortened  by  an  increase 
(when  these  temperatures  are  between  about  42°  and  72°  F.) ;  the  differ- 
ence in  longevity  of  a  species  at  different  temperatures  corresponding 
roughly  to  the  difference  in  temperature.     (J.  P.  Baumberger.) 


INSECT   ECOLOGY 


355 


Development  in  General.^The  effects  of  temperature  on  the 
development  of  insects  are  known  in  a  qualitative  way,  and  considerable 
progress  has  been  made  in  the  quantitative  study  of  the  subject.  At 
a  certain  degree  of  low  temperature  during  development  an  insect 
becomes  physiologically  inactive,  or  dormant,  without  being  killed, 
and  may  resume  activity  when  the  temperature  rises.  This  point 
is  termed  the  threshold  of  development  {critical  point,  developmental 
zero).  Temperatures  above  this  point  that  are  conducive  to  develop- 
ment are  termed  effective  temperatures,  and  in  ascertaining  the  number 
of  temperature  units  requisite  to  development,  all  temperatures  below 
the  threshold  of  development  are  disregarded.  The  effects  of  high 
temperatures  in  accelerating  development,  and  of  low  temperatures  in 
retarding  development,  are  known  to  all  who  have  raised  butterflies 
or  moths  from  pupae. 

The  theory  used  to  be  that  the  entire  development  of  an  insect, 
from  the  time  the  egg  is  laid  until  the  adult  emerges,  requires  a  fixed 
number  of  effective  degrees  of  temperature;  the  same  being  true  also 
for  any  stage  of  the  insect,  as  egg,  larva  or  pupa;  that  the  entire  develop- 
ment, or  any  phase  of  the  development,  will  not  be  completed  until  a 
definite  number  of  temperature  units  have  been  experienced,  whether 
the  time  required  be  long  or  short.  The  number  expressing  the  total 
temperature,  or  temperature  constant,  is  obtained  by  multiplying  the 
mean  daily  temperature  by  the  number  of  days  required  for  the  develop- 
ment. Needless  to  say,  the  effects  of  temperature  are  obscured  by 
those  of  humidity,  light,  and  several  other  influences  in  nature,  and 
become  evident  only  under  the  exact  conditions  of  experimentation. 

For  the  development  of  the  boll  weevil,  Hunter  and  Hinds  (1905) 
give  the  following  summary: 


Average 

Average  1 

Total 

1        Total 

period 

effective 

effective 

Stage 

observations 

for  stage, 

temperature, 

temperature, 

Days 

°F. 

°F. 

Egg 616 

4.0 

34-0 

136.0 

Larva 313 

9.8 

32.2 

315-6 

Pupa 530 

S-S 

33-2 

182.6 

Total  development,  sum  of  stages          i ,  459 

193 

32.9 

634.2 

Observations  on  entire  period  of 

development 887 

19.6 

32.2 

632.0 

temperati 


356  ENTOMOLOGY 

Exact  experimental  studies  of  the  effects  of  temperature,  moisture, 
and  other  conditions  have  undoubtedly  an  important  economic  bearing. 
For  example:  it  was  found,  from  experiments  made  by  Professor.  T.  J. 
Headlee  in  Manhattan,  Kansas,  that  the  cycle  of  the  codUng  moth 
required  an  average  of  39  days  with  an  average  of  1,006  degrees  of 
effective  temperature  (temperatures  above  the  threshold  of  develop- 
ment, given  at  that  time  as  about  50°  F.).  With  as  exact  a  knowledge 
of  the  other  factors,  particularly  moisture,  one  ought  to  be  able,  with 
the  aid  of  weather  reports,  to  foretell  when  a  given  brood  of  the  cod- 
ling moth  will  appear;  which  would  evidently  be  of  advantage  to 
fruit-growers. 

The  subject  is,  however,  not  so  simple  as  it  was  thought  to  be. 
Sanderson  (1908,  1910),  who  has  given  a  useful  discussion  of  this  sub- 
ject, showed  "that  upon  purely  theoretical  grounds  there  could  be 
no  uniform  accumulation  of  temperature  or  'thermal  constant'  for  the 
various  stages  of  insect  growth,  but  that  the  relation  of  temperature  to 
growth  phenomena  was  probably  different  for  each  species  and  might 
be  expressed  by  a  curve,  the  abscissas  of  which  represent  degrees  of 
temperature  and  the  ordinates  represent  the  time  factor.  The  impor- 
tance of  considering  the  so-called  law  of  the  velocity  of  chemical  reaction 
as  influenced  by  temperature  was  pointed  out  and  it  was  shown  that  the 
velocity  of  reaction  varies  at  different  temperatures.  It  was  shown 
that  both  the  so-called  thermal  constant  and  coefficient  of  velocity 
increase  as  the  temperature  is  lowered  from  the  optimum  of  the  species, 
and  that  the  curve  for  each  species  and  phase  of  growth  or  activity  of 
that  species  must  be  plotted  before  the  influence  of  temperature  can  be 
exactly  stated."  Sanderson  defined  the  "  thermal  constant"  for  insects 
as  "that  accumulation  of  mean  daily  temperature  above  the  'critical 
point'  of  the  species,  which  will  cause  it  to  emerge  from  hibernation  or 
to  transform  from  any  given  stage."  (i)There  is  no  uniform  minimum 
above  which  the  temperature  may  be  accumulated  as  effective,  but  this 
varies  with  each  species  and  phase  of  growth;  (2)  there  is  no  "thermal 
constant"  as  far  as  a  mere  accumulation  of  temperatures  is  concerned; 
and  (3)  the  velocity  of  reaction  varies  according  to  the  range  of  tem- 
peratures (Sanderson) .  To  illustrate  the  first  of  these  three  statements, 
Sanderson  cites  the  green-bug,  Toxoptera  graminum,  which,  as  Hunter 
and  Glenn  showed,  begins  to  develop  at  1.65°  C,  while  its  parasite, 
Lysiphlebus  tritici,  shows  no  activity  below  about  4°  or  5°  C.  For  the 
bollworm  the  point  of  cold  rigor  is  about  10°  C.  In  regard  to  the  second 
statement,  Sanderson  adds:  "It  is  evident  that  any  accumulation  of 


INSECT   ECOLOGY  357 

temperature  to  secure  a  thermal  or  physiological  constant  cannot  be 
based  on  a  mere  addition  where  variable  temperatures  are  involved,  for 
it  is  evident  that  every  degree  has  a  different  value  in  relation  to  the 
time  factor.  Thus  as  the  mean  temperature  rises  with  the  advance  of 
the  season  both  the  time  for  the  pupal  stage  and  the  total  accumulated 
temperature  for  the  pupal  stage  of  the  codhng  moth  decrease  with  the 
advancing  season.  Though  a  fairly  constant  'total  effective  tem- 
perature' for  any  given  phase  of  an  insect's  hfe  or  activity  may  be 
secured  for  the  summer  months  when  there  is  a  fairly  constant  mean 
temperature,  such  an  accumulation  will  have  no  meaning  in  regard 
to  the  same  phenomena  in  spring  and  fall  when  the  temperatures  are 
more  variable.  If  we  wish  to  be  exact,  we  must  secure  the  temperature 
curve  for  the  species,  based  on  the  observation  of  a  considerable  num- 
ber of  individuals  kept  at  different  constant  temperatures,  or  possibly 
better  at  temperatures  having  a  diurnal  variation  with  constant  maxi- 
mum and  minimum,  and  with  fairly  constant  moisture  conditions." 

Krogh  on  Temperature-velocity.— The  results  obtained  by  Krogh, 
which  differ  in  some  respects  from  those  of  other  investigators,  are 
regarded  as  highly  important.  He  finds  that  the  temperature-velocity 
curve  expressing  the  rate  at  which  segmentation  takes  place  in  frog's 
eggs  is,  between  7°  and  20.7°,  a  straight  line.  "An  increase  in  tem- 
perature between  these  limits  produces  a  proportional  increase  in  the 
velocity  with  which  the  processes  in  the  egg  leading  up  to  segmentation 
take  place.  Below  7°  the  curve  deviates  from  the  straight  line  and  the 
reaction  takes  place  more  rapidly  than  one  would  expect  from  the 
results  obtained  at  higher  temperatures.  At  the  lowest  temperature, 
where  the  development  certainly  is  no  longer  normal  the  curve  turns 
downward  once  more." 

"The  relation  between  the  temperatures  and  the  velocity  of  embry- 
onic development  is  algebraic  over  a  range  of  temperatures  which 
corresponds  approximately  to  that  at  which  normal  development  can 
take  place,  and  the  curve  representing  the  relation  is  consequently  a 
straight  Hne."  The  velocity  of  embryonic  development  is  a  linear 
function  of  the  temperature. 

In  regard  to  the  relation  between  temperature  and  the  later  stages  of 
development  of  the  frog,  Krogh  says:  "Between  the  temperatures  12° 
and  25°  the  increment  in  velocity  of  the  embryonic  development  of  the 
frog  is  therefore  proportional  to  the  temperature  increment,  but  below 
12°  the  development  is  more  rapid  than  one  would  expect  from  the 
formula." 


358  ENTOMOLOGY 

Concerning  the  time  of  incubation  of  the  eggs  of  a  water  beetle, 
Acilius  sulcatus,  Krogh  found  that  "when  the  reciprocal  values  of  the 
hatching  times  at  the  three  temperatures  are  plotted  against  the  tem- 
peratures, they  are  found  to  lie  in  a  straight  line."  (See  also  Krogh's 
results  on  Pupal  Development,  p.  359.) 

From  all  that  has  been  said,  then,  it  appears  that  there  is  a  threshold 
of  development,  which  varies  for  different  species  and  under  different 
conditions  of  existence,  and  that  there  is  such  a  thing  as  an  accumulation 
of  effective  temperatures,  or  thermal  constant.  This  constant  is  lim- 
ited, however,  to  a  certain  range  of  temperature,  below  which  growth  or 
development  is  faster  than  the  constant  requires,  and  above  which  it  is 
slower.  This  fact  has  an  economic  consequence;  for  basing  predictions 
upon  the  thermal  constant  alone,  the  spring  brood  of  the  codHng  moth 
or  other  insect  would  appear  earlier  than  would  be  expected,  and  the 
autumn  brood  later. 

Reproduction. — Among  plant  lice  parthenogenesis  (reproduction 
without  fertilization)  is  apparently  continuous  and  uninterrupted  under 
favorable  environmental  conditions;  amphigony  (reproduction  by  fertili- 
zation) occurring  only  under  the  influence  of  low  temperatures  and, 
as  certain  authors  claim,  inadequate  food  supply.  Aphids  in  tropical 
and  other  warm  climates  appear  to  have  the  tendency  to  reproduce 
exclusively  by  parthenogenesis.  The  same  condition  apparently  obtains 
among  greenhouse  aphids  in  temperate  climates.  Aphids  in  colder 
climates  undergo  heterogony  (reproduction  both  by  parthenogenesis 
and  amphigony)  as  an  adaptation  to  adverse  environmental  conditions. 
In  certain  species,  the  appearance  of  the  amphigonous  generation  seems 
to  be  a  rhythmic  process,  which  continues  to  occur  at  definite  cyclical 
intervals  for  some  time  after  the  influence  of  low  temperature  has  been 
eliminated.     (L.  B.  Uichanco.) 

Incubation. — The  length  of  the  egg  period  varies  greatly  according 
to  surrounding  conditions,  chiefly  those  of  temperature.  First  brood 
eggs  of  the  codHng  moth  in  Michigan  hatched  at  outdoor  temperatures 
in  4  to  10  days,  average  8  days,  at  an  average  mean  temperature  of 
about  67.6°  F.;  eggs  not  hatching  readily,  however,  during  extremely 
dry  weather.     (A.  G.  Hammar.) 

In  regard  to  the  eggs  of  this  species,  C.  B.  Simpson  says:  " (i)  Under 
a  low  temperature  the  length  of  the  egg  stage  is  longer  than  at  high 
temperatures.  (2)  Under  normal  field  conditions  a  small  difference 
in  temperature  causes  but  Httle  change  in  the  length  of  the  stage.     (3) 


INSECT    ECOLOGY  359 

The  eggs  are  not  in  the  same  stage  of  maturity  at  the  time  of  oviposition, 
as  at  24°  F.  we  have  from  9  to  i8  days  as  the  length  of  the  stage." 

As  regards  the  threshold  of  development,  Sanderson  found  that  eggs 
of  the  meal  worm,  Tenehrio  molitor>  failed  to  hatch  at  9°  or  10°  C.  but 
hatched  at  12°  C. 

The  time  from  the  deposition  of  the  eggs  to  hatching  of  the  chinch 
bug'  is  variable,  being  longer  if  temperature  is  low,  or  shorter  if  high. 
Thus  first  brood  eggs  (June)  with  an  average  mean  temperature  of  73°  F. 
hatch,  in  17.3  days;  and  second  brood  eggs  (August)  at  76.58°  F.  in  11.45 
days;  the  average  for  both  broods  being  14.4  days  (Headlee  and 
McCoUoch). 

Larval  Development. — The  discussion  already  given  of  growth  and 
development  in  relation  to  temperature  applies  of  course  to  the  larval 
stage  as  well  as  to  all  other  stages  of  development. 

Larvae  of  the  cotton  boll  weevil  in  squares  developed  in  7  days  at 
an  average  mean  temperature  of  75°  F.;  the  total  of  effective  tem- 
peratures being  280  degrees  F.     (Hunter  and  Hinds.) 

The  bollworm,  or  corn  ear  worm,  developed  in  21  days  at  an  average 
mean  temperature  of  77°  F.;  the  total  of  effective  temperatures  being 
617  degrees  F.     (Quaintance  and  Brues.) 

In  these  experiments  it  was  assumed,  as  was  formerly  customary, 
that  only  temperatures  above  43°  F.  were  effective  for  growth;  this  is 
known  to  be  a  mistake.  A  small  percentage  of  boll  worms  survive 
a  temperature  of  34°  F. ;  but  larvae  subjected  to  temperatures  somewhat 
below  freezing  for  one  to  two  days  are  killed  outright. 

A  constant  temperature  of  90°  F.  prevents  the  development  of  the 
plant  louse.  Aphis  avence;  the  optimum  temperature  for  the  production 
of  the  wingless  agamic  forms  being  about  65°  F.     (H.  E.  Ewing.) 

Warmth  and  dryness  are  favorable  to  the  development  of  species 
of  "thrips"  (Thysanoptera)  and  of  the  "red  spider,"  a  well  known 
mite  that  injures  plants,  especially  in  greenhouses. 

Molting. — In  the  walking-stick,  Diapheroirtera  Jemorata,  a  low  tem- 
perature lengthens,  while  a  high  temperature  shortens,  on  an  average, 
the  interval  between  molts.  A  low  temperature  has  a  tendency  to 
decrease  the  number  of  molts,  while  a  high  temperature  increases  the 
number.      (H.  H.  P.  and  H.  C.  Severin.) 

Pupal  Development. — Krogh  found  that  the  extremely  simple 
relation  (already  described)  between  temperature  and  the  velocity  of 
embryonic  development  held  good  also  for  the  changes  taking  place 
during  the  pupal  life  of  the  meal  worm,  Tenehrio  molitor.     He  says: 


360  ENTOMOLOGY 

(i)  "The  relation  between  the  temperature  and  the  velocity  of  pupal 
development  in  Tenehrio  cannot  be  expressed  in  terms  of  Van't  Hoff's 
formula,  but  between  18.5°  and  28°  the  relation  is  algebraic  and  the  curve 
representing  it  is  a  straight  line.  (2)  Beyond  these  hmits  the  curve 
is  not  straight,  but  bends  upwards  at  the  lower  temperature  and  down- 
wards at  the  higher.  Normal  development  is  still  possible  at  tempera- 
tures between  15°  (13.5°)  and  2,^,°.  (3)  In  the  metaboHc  activity  of  the 
chrysalides  of  Tenehrio  three  stages  are  recognizable,  corresponding 
roughly  to  periods  of  disintegration  of  larval  tissues,  comparative  rest 
and  formation  of  imago  tissues.  The  metaboHsm  in  the  tissue  disin- 
tegration period  is  practically  of  the  same  intensity  as  in  the  tissue  for- 
mation period.  (4)  The  total  amount  of  CO2  produced  during  the  pupal 
life  is  the  same  at  all  the  temperatures  examined  (2i°-33°).  There  is 
no  optimum  temperature  with  regard  to  metabolism.  The  relation  be- 
tween the  temperature  and  the  average  CO2  production  per  hour 
follows  the  same  curve  as  that  found  for  the  velocity  of  development. " 

Sanderson  found  that  pupae  of  the  meal  worm,  Tenehrio  molitor, 
failed  to  transform  at  9°  or  10°  C.  but  transformed  at  12°  C;  and  that 
pupae  of  the  codling  moth  underwent  little  development  below  55°  F. 
As  a  rule,  the  length  of  the  pupal  period  is  rapidly  shortened  by 
increase  of  temperature.  In  Michigan,  in  spring,  pupae  of  the  codling 
moth  developed  in  an  average  of  18.4  days  at  an  average  mean  tempera- 
ture of  66°  F.  (A.  G.  Hammar.)  The  boll  weevil  in  summer  had  a  pupal 
period  of  5.1  days  at  an  average  mean  temperature  of  74.3°  F.  (Hunter 
and  Pierce.) 

Life  Cycle. — The  total  hfe  cycle  of  the  boll  weevil,  as  obtained  by 
adding  egg,  larval,  and  pupal  periods,  was  found  to  be  17.65  days,  at 
an  average  mean  temperature  of,77.8°  F.;  or  an  average  of  effective 
temperaturesof  34.8  degrees;  the  total  of  effective  temperatures  being 
614.2  degrees.  As  found  by  continuous  observations  on  the  same  indi- 
viduals, the  life  cycle  was  17.7  days,  with  average  mean  temperature  76.9° 
F.;  average  of  effective  temperatures  33.9  degrees,  and  total  of  effective 
temperatures  600  degrees.  (Hunter  and  Hinds.)  Here,  again,  43°  F. 
was  assumed  to  be  the  "  zero  of  development." 

Acclimatization. — A  few  insects  have  become  adapted  to  survive  and 
thrive  under  extremely  high  temperatures.  Larvae  of  a  fly,  Stratiamys, 
have  been  found  in  a  hot  spring  in  Colorado  with  a  temperature  of  69°  C. 
A  water  beetle  in  India  was  found  in  a  warm  spring  at  44.4°  C.  Few 
organisms,  however,  resist  temperatures  over  45°  C.  (Dr.  C.  B.  Daven- 
port.)    Probably  in  successive  generations  of  the  ancestors  of  these  forms 


INSECT   ECOLOGY  361 

there  were  some  individuals  that  could  endure  a  little  more  heat  than 
the  others,  and  gradually  a  resistant  strain  of  a  species  was  built  up. 

Hibernation. — Temperature  manifestly  bears  an  important  relation 
to  hibernation,  the  phenomenon  of  passing  the  winter  in  seclusion, 
usually  in  a  quiescent  or  inactive  condition.  The  stimulus  leading  to 
hibernation  is  usually  decreased  temperature  in  autumn.  Thus  the 
cotton  boll  weevil  begins  to  hibernate  with  the  decrease  in  mean  average 
temperature  to  about  55°.  (Hinds  and  Yothers.)  Low  temperature  is 
not  always,  however,  the  immediate  incentive  to  hibernation.  The 
codling  moth  larva  begins  to  hibernate  before  the  temperature  falls 
and  before  food  fails.  The  woolly  bear  caterpillars  {Isia  isabella)  show 
great  regularity  in  the  date  at  which  they  stop  feeding,  under  con- 
ditions of  high  temperature,  different  degrees  of  relative  humidity, 
and  an  abundance  of  fresh  food.  (Baumberger.)  Mosquitoes  begin  to 
hibernate  before  cold  weather  sets  in.  Among  other  influences  there 
may  be  a  "tendency"  to  hibernate  in  many  species. 

The  period  of  hibernation  is  prolonged  by  low  temperatures.  The 
emergence  of  Cecropia  moths  from  their  cocoons  may  be  delayed  for 
more  than  one  year  by  placing  the  cocoons  in  cold  storage  with  the 
temperature  a  little  above  the  freezing  point. 

Warm  periods  during  winter  may  arouse  insects  to  more  or  less 
activity.  It  is  commonly  thought  by  collectors  that  a  uniformly 
cold  winter  is  more  favorable  to  a  subsequent  abundance  of  insect  life 
than  a  winter  interrupted  by  mild  spells. 

Some  insects  do  not  awaken  easily  from  the  condition  of  hibernation, 
while  others  respond  readily  to  an  increase  of  temperature.  Examples 
of  the  latter  kind  are  the  pomace  flies  {Drosophila),  the  house  fly  {Musca 
domeslica)  and  other  flies,  and  cockroaches. 

The  temperature  requisite  to  emergence  varies  with  the  species. 
The  boll  weevil,  in  hibernation  by  the  time  of  the  first  hard  frost,  con- 
tinues to  hibernate  until  the  mean  average  temperature  has  been  for 
some  time  above  65°  F.  (Hunter  and  Hinds.)  In  the  case  of  the  brown- 
tail  moth  34°  F.  is  the  threshold  above  which  the  temperature  accumu- 
lates in  determining  the  time  of  emergence  of  the  caterpillars  from  their 
winter  nests.     (Sanderson.) 

According  to  J.  P.  Baumberger,  insects  hibernate  as  (i)  adults, 
when  their  food  habits  are  such  that  oviposition  can  take  place  on  the 
proper  food  at  the  earliest  warm  weather;  (2)  as  larvae,  when  protected 
from  the  cold  and  thus  able  to  continue  feeding  to  the  latest  date  pos- 
sible; (3)  as  pupae  or  eggs,  because  they  are  nonfeeding  resistant  stages. 


362  ENTOMOLOGY 

,  Many  examples  of  adaptation  in  relation  to  winter  conditions  will 
suggest  themselves.  Insects  when  about  to  hibernate  seek  shelter  or 
construct  shelter,  or  both.  They  may  simply  crawl  into  existing 
crevices  or  holes,  as  in  the  ground  or  in  plants,  under  stones,  logs,  loose 
bark,  dead  leaves,  among  stems  or  roots  of  plants,  or  may  burrow  into 
the  ground  or  into  Hving  or  dead  plants;  or  may  miake  cocoons  or  silken 
nests  or  earthen  cells,  in  which  protection  is  afforded  by  surrounding  air- 
spaces. A  curious  situation  for  hibernation  is  that  of  back-swimmers 
(Notonecta) ,  which  have  been  found  clustered  in  small  cavities  in  thick 
ice.  Hibernating  insects  protect  themselves  more  or  less  successfully 
from  such  adverse  inifluences  as  sudden  changes  of  temperature,  excess 
of  moisture  or  of  dryness,  invasion  by  fungi  and  bacteria,  and  from 
attacks  by  other  insects  or  by  birds  or  mammals. 

There  are,  however,  many  examples  of  unsuccessful  hibernation. 
Exceptionally  low  temperatures  occasionally  exterminate  the  boll  weevil 
in.  certain  areas,  the  mortality  being  increased  by  excessive  rainfall. 
Concerning  the  caterpillars  of  the  brown-tail  moth  in  their  winter  nests, 
Sanderson  says  that  where  nests  of  average  size  containing  300-400 
larvae  were  subjected  to  —24°  F.  or  lower,  from  72  to  100  per  cent,  of 
the  larvae  were  killed,  but  that  in  large  nests  from  the  same  locaHty  only 
57  per  cent,  were  killed;  the  larvae  in  the  outer  parts  of  the  nests  dying 
first. 

Following  a  period  of  subnormal  temperatures  in  the  state  of 
Washington,  1919,  examinations  were  made  of  larvae  of  the  codHng  moth 
under  bark  or  burlap  bands.  It  was  found  that  wherever  the  minimum 
temperature  had  been  lower  than  —25°  F.  all  larvag  were  killed.  On 
higher  ground,  where  the  minimum  temperatures  ranged  from  —20°  to 
—  25°,  80  to  90  per  cent,  of  the  larvae  were  killed.  On  still  higher 
ground,  with  minimum  temperatures  of  —15°  to  —20°,  the  mortality 
was  approximately  70  per  cent.  One  interesting  fact  noted  was  that 
frequently,  on  tearing  away  the  burlap  band,  one  or  two  living  larvae 
would  be  found  in  the  midst  of  a  number  of  dead  ones.  It  seems  impos- 
sible, in  these  cases,  that  the  living  larvae  had  any  more  protection  than 
the  others.  They  must  simply  have  had  more  vitality.  (E.  J.  New- 
comer.) 

Distribution. — Minimum  temperatures  exert  an  important  influence 
in  hmiting  the  northern  distribution  of  insects,  according  to  Sanderson, 
from  whose  article  on  the  subject  the  following  extracts  have  been  taken. 
In  New  Hampshire  (January,  1907)  most  of  the  hibernating  caterpillars 
of  the  brown-tail  moth  (excepting  those  in  large  nests)  were  killed  off  by 


INSECT   ECOLOGY  363 

a  temperature  of  —  24°  F.  and  below.  The  northern  Hmit  of  the  San 
Jose  scale  insect  corresponds  approximately  with  the  average  annual 
minimum  isotherm  of  —15°  F.  This  species  dies  out  in  central  Wis- 
consin and  cannot  survive  in  Minnesota.  The  wide-ranging  cotton 
bollworm,  or  corn  ear  worm,  does  not  winter  in  Minnesota  and  no  records 
of  injury  occur  in  Montana,  Wyoming  or  the  Dakotas.  The  harlequin 
cabbage  bug  maintains  a  foothold  in  the  latitude  of  Long  Island, 
southern  Ohio  and  southern  Illinois,  but  has  been  unable  to  extend 
its  permanent  range  farther  north  on  account  of  being  killed  off  by  cold 
during  hibernation. 

A  blanket  of  snow  may  offset  the  effects  of  minimum  temperatures, 
as  with  the  striped  cucumber  beetle,  which  hibernates  in  the  soil,  the 
codling  moth,  which  passes  the  winter  as  a  caterpillar  in  a  cocoon  under 
bark,  the  scale  insects,  and  many  other  species. 

Occasional  periods  of  extremely  low  temperature,  occurring  at 
long  intervals,  are  temporary  checks  upon  the  distribution,  but  the 
exact  northern  limits  of  distribution  depend  rather  upon  the  average 
minimum  temperature. 

Pressure 

From  the  few  observations  that  have  been  made  upon  the  subject  it 
appears  that  insects  are  sensitive  to  variations  in  atmospheric  pressure, 
as  birds  and  mammals,  including  man,  are  said  to  be.  Atmospheric 
pressure  as  correlated  with  humidity  affects  animals  indirectly  through 
its  effects  on  evaporation.  Thus  high  pressure  with  low  humidity 
means  increased  evaporation,  and  vice  versa. 

The  following  extracts  are  from  an  interesting  article  by  D.  C.  Par- 
man  on  the  effect  of  storm  phenomena  on  insect  activity. 

With  a  rapidly  falling  barometer  several  species  of  flies  (Muscidae) 
first  become  nervously  active  and  then  go  into  a  state  of  partial  coma, 
in  which  state  they  are  more  subject  to  the  action  of  other  destructive 
agencies,  diseases  probably  included.  The  decrease  in  the  number  of 
flies  is  quite  appreciable  after  a  severe  tropical  storm. 

The  adults  of  the  fly  Chrysomyia  macellaria  apparently  will  not  chill 
and  die  under  the  effect  of  a  rising  barometer  as  under  a  lowering  baro- 
metric pressure. 

Insects  attracted  to  hghts  are  more  active  during  high  barometric 
periods  and  especially  while  the  barometer  is  rising. 

Bred  adult  Diptera  tend  to  emerge  on  periods  of  rising  barometer. 


364  ENTOMOLOGY 

The  hea\y  emergences  apparently  always  have  been  during  periods  of 
high  barometric  pressure.  Trappings  and  observations  indicate  that 
muscoid  Diptera  are  most  abundant  during  long  periods  with  slight 
variations  in  barometric  pressure,  provided,  of  course,  temperature, 
humidity  and  rainfall  are  favorable. 

Migration  of  the  butterfly,  Hypatus  bachmani  was  observed  during 
the  summer  and  fall  of  19 16  to  take  place  after  storms,  which  indicates 
that  the  flights  were  during  high  barometric  pressure. 

Moisture 

Moisture  ranks  with  temperature  as  a  highly  essential  condition  of 
existence.  Moisture  affects  terrestrial  animals  most  vitally  through 
evaporation,  which  will  be  considered  beyond.  Here  we  may  state 
the  effects  of  moisture  without  special  reference  to  evaporation,  but  it 
should  be  borne  in  mind  that,  in  most  of  the  phenomena  discussed, 
evaporation  is  an  important  factor. 

Metabolism. — "Water  plays  a  part  in  growth  second  in  importance 
to  no  other  agent,  so  that  in  its  absence  growth  cannot  occur.  As  the 
quantity  is  increased,  growth  is  increased  until  an  optimum  is  reached. 
The  amount  imbibed  does  not,  however,  depend  directly  upon  the 
amount  available,  but  rather  upon  the  needs  and  habits  of  the 
species."     (Dr.  C.  B.  Davenport.) 

I.  There  is  an  optimum  moisture  for  insect  development.  2.  This 
optimum  is  not  the  same  for  different  species.  3.  The  moisture  which 
may  hasten  the  development  of  one  species  may  retard  the  develop- 
ment of  another.  (Bachmetjew.)  Headlee  adds  that  the  rate  of 
metabolism  in  certain  actively  feeding  insects  with  an  abundant  supply 
of  succulent  food  is  not  affected  by  large  differences  in  atmospheric 
moisture.  He  found  that  the  green-bug,  Toxoptera  graminum,  required 
six  days  to  pass  from  birth  to  maturity  under  a  constant  temperature  of 
80°  F.  and  relative  humidities  of  37,  50,  70,  80  and  100  per  cent.  Pro- 
fessor Headlee  found  also  that,  with  the  angoumois  grain  moth  and  the 
bean  weevil  (i)  increase  in  atmospheric  humidity  means  increase  in 
speed  of  metabolism  as  measured  by  length  of  Ufe  cycle;  (2)  the  optimum 
per  cent,  of  atmospheric  humidity  is  the  highest  which  will  not  encour- 
age a  heavy  growth  of  fungi;  (3)  100  per  cent,  atmospheric  humidity 
destroys  by  encouraging  the  growth  of  fungi,  and  low  atmospheric  mois- 
ture destroys  directly — probably  by  the  extraction  of  water;  (4)  while 
the  egg  stage  of  the  bean  weevil,  at  least,  is  most  sensitive  to  the  effect 


INSECT   ECOLOGY  365 

of  low  atmospheric  humidity,  other  stages  are  unfavorably  affected; 
(5)  low  atmospheric  moisture  might  be  developed  into  an  efficient  in- 
secticide for  certain  species  of  stored  grain  insects. 

Eclosion. — Moisture  frequently  determines  the  time  of  eclosion, 
or  the  emergence  of  an  insect  from  the  pupa.  Hessian  flies  do  not 
emerge  from  the  puparia  in  dry  weather,  but  issue  in  abundance  after 
rainfall  in  the  proper  season.  When  bred  indoors,  the  flies  do  not 
emerge  from  dry  soil,  even  though  the  temperature  be  favorable,  but 
emerge  shortly  when  the  soil  is  moistened. 

Activity. — Wet  weather  lessens  the  activities  of  insects  exposed  to 
it.  There  are  some  exceptions,  however.  Larvae  of  the  midges,  Itoni- 
didae,  are  all  very  sensitive  to  the  presence  of  moisture,  to  which  they 
react  positively.  Larvae  of  the  clover  seed  midge  emerge  from  the  clo- 
ver heads  usually  in  damp  weather  and  often  in  large  numbers  when  the 
plants  are  wet  with  rain.  Even  when  full  grown  and  contracted  in 
readiness  to  form  the  puparium,  they  revive  and  move  about  if  mois- 
tened with  water. 

Oviposition. — It  has  been  found  that  with  the  house  fly,  when 
temperatures  are  high  or  moderately  high,  increased  humidity  hastens 
egg-laying.  This  may  be  partially  due  to  the  effect  of  humidity  on 
the  food  and  breeding  substances — keeping  them  moist  and  attractive. 
(Bishopp,  Dove,  Parman.) 

Mortality.— Changes  in  relative  humidity  produce  striking  changes 
in  the  mortality  of  Drosophila,  the  mortality  increasing  with  a  decrease 
of  humidity,  the  optimum  humidity  being  loo  per  cent.  The  effects 
of  low  humidity  on  mortality  are  most  marked  with  very  youngpupae, 
whose  covering  permits  a  rapid  evaporation  of  body  moisture.  After 
a  few  hours,  when  integumental  changes  making  evaporation  more 
difficult  have  set  in,  the  eft'ects  of  low  humidity  are  correspondingly 
decreased.     (A.  Elwyn.) 

Hibernation. — As  a  preparation  for  hibernation,  the  water  content 
of  an  organism  is  frequently  reduced;  as  also  in  seeds  or  spores.  Thus 
the  Colorado  potato  beetle  loses  about  30  per  cent,  of  its  gross  weight 
through  the  loss  of  water,  which  enables  it  to  withstand  a  lower  freezing 
point  and  higher  temperatures  than  if  the  protoplasm  were  not  thus 
condensed.  (Tower.)  As  Sanderson  notes,  the  time  of  emergence  from 
hibernation  is  controlled  by  moisture  conditions  as  well  as  temperature, 
or  independent  of  temperature.  Tower  kept  potato  beetles  for  eight- 
een months  at  a  high  temperature,  but  with  a  dry  atmosphere,  and 
they  emerged  as  soon  as  normal  moisture  conditions  were  produced. 


366  ■  ENTOMOLOGY 

-Estivation. — In  the  case  of  the  potato  beetle,  hibernation  and  (esti- 
vation, or  the  condition  of  dormancy  in  summer,  are  practically  the  same 
as  regards  the  Hfe  history  of  the  insect,  according  to  Tower.  In  the 
tropics,  where  there  is  no  hibernation,  aestivation  occurs  over  the  dry 
season.  Though  aestivation  is  associated  mainly  with  heat,  relative 
humidity  is  also  a  factor,  and  "undoubtedly  has  the  most  important 
influence  upon  the  time  of  emergence  of  forms  in  aestivation  during 
the  summer  or  in  arid  regions.  (Sanderson.)  During  intense  heat  (95° 
to  122°  F.)  the  boll  weevil  aestivates  temporarily  on  the  ground  under 
protecting  objects. 

Drought. — ^Drought  accompanies  heat  and  affects  animals  and 
plants  through  evaporation.  It  affects  them  directly,  by  desiccation; 
or  indirectly,  by  drying  out  the  food  plants  or  other  food  substances; 
as  with  larvae  of  the  boll  weevil  or  the  house  fly.  The  range  of  dryness 
within  which  insects  can  exist  varies  greatly  with  different  species. 
The  chinch  bug,  unlike  the  Hessian  fly,  thrives  in  hot  dry  summers; 
and  species  that  inhabit  arid  regions  are  exceptionally  resistant  to 
conditions  of  drought. 

Precipitation. — Rainfall  is  direct  or  indirect  in  its  influence  on  the 
life  and  activities  of  insects.  Eggs  of  the  cotton  boll  worm  are  destroyed 
in  immense  numbers  by  the  mechanical  force  of  the  rain  during  violent 
storms.  The  combined  effects  of  rain,  wind,  and  sandy  particles 
washed  against  the  plants  removes  many  eggs .  (Quaintance  and  B rues .) 
Young  larvae  of  the  bollworm  feeding  on  corn  early  in  the  spring  are 
often  washed  down  by  rain  and  submerged  for  considerable  periods. 
Of  twenty  newly  hatched  larvae  submerged  for  seventeen  hours,  all 
but  four  survived  the  immersion.  Larger  larvae  cannot  stand  such 
long  periods,  but  when  dropped  into  water  become  stupefied  after  a  few 
minutes.  Pupae  could  not  withstand  twenty-four  hours'  submergence 
in  rain  water  at  normal  summer  temperatures,  but  at  a  temperature  of 
from  50°  to  60°  F.  they  were  unharmed  by  from  four  to  six  days' 
submergence.  (Quaintance  and  Brues.)  In  the  case  of  the  cotton  boll 
weevil,  a  pupa  survived  an  immersion  of  six  hours;  and  60  per  cent,  of 
adults,  one  of  fifteen  hours.  Ten  adults  were  floated  for  one  hun- 
dred and  twelve  hours,  after  which  only  one  was  dead,  but  only  two 
were  normal;  after  floating  for  only  twenty-five  hours,  however,  six  of 
the  ten  were  normal.  The  floating  of  adults  and  infested  squares  ex- 
plains the  appearance  of  weevils  in  great  numbers  along  high-water 
line  immediately  after  a  flood.     (Hunter  and  Hinds.) 

Rains  favor  weevil  increase  in  several  ways.     Frequent  rains  in- 


INSECT   ECOLOGY  367 

crease  the  growth  of  the  plant  and  lead  to  the  production  of  a  larger 
number  of  squares  which  may  become  infested.  Driving  rains  knock 
off  infested  squares,  and  by  softening  and  moistening  the  food  hasten 
the  development  of  the  larvas  within.  Squares  which  are  already  upon 
the  ground  are  protected  during  rainy  weather  from  sunshine  and  dry- 
ing. Rain  hinders  the  enemies  of  the  weevil  far  more  than  it  does  the 
development  of  the  weevils  themselves.  On  the  other  hand,  it  seems 
probable  that  as  many  of  the  hibernating  weevils  perish  from  frequent 
wetting  as  from  exposure  to  the  cold.     (Hunter  and  Hinds.) 

Frequent  heavy  rains  in  spring  reduce  greatly  the  numbers  of 
immature  chinch  bugs. 

Moisture  increases  the  mortality  of  insects  indirectly  by  favoring 
the  growth  of  parasitic  fungi  or  bacteria.  Thus,  in  moist  weather 
chinch  bugs  may  be  almost  exterminated  by  the  fungus  Sporotrichum, 
as  described  with  other  examples  in  a  preceding  chapter.  (See 
page  218.) 

This  chinch  bug  fungus  will  not  grow  in  a  relative  humidity  of  90 
per  cent,  or  less,  but  will  remain  dormant  in  the  spore  stage  for  an  indefi- 
nite period  (more  than  eighteen  months,  in  dryness.)  The  fungus  can 
hardly  have  too  much  moisture  in  a  state  of  nature;  dashing  and  wash- 
ing rains  serving  merely  to  distribute  it.     (Headlee  and  McColloch.) 

Composition 

The  fact  that  animals  require  oxygen  for  respiration,  and  give  off 
carbon  dioxide,  while  plants  utihze  carbon  dioxide  and  set  free  oxygen, 
need  only  be  alluded  to. 

The  chief  constituents  of  air  are  oxygen,  nitrogen,  carbon  dioxide, 
water-vapor  in  varying  amounts,  with  small  quantities  of  gaseous 
ammonia  and  hydrogen  dioxide,  and  extremely  small  amounts  of  argon. 
The  organic  matters  present,  as  bacteria,  spores  of  fungi,  pollen  grains, 
etc.,  are  highly  important  biologically. 

In  atmospheric  air  there  are  very  nearly  three  parts  of  nitrogen  to 
one  part  of  oxygen,  whether  by  volume  or  by  weight;  with  slight  varia- 
tions in  these  proportions. 

The  carbon  dioxide  is  present  in  relatively  small  quantity,  about 
three  parts  in  ten  thousand,  the  proportion  varying  according  to  the 
locality  and  season;  being  greater  in  cities  than  in  the  country;  in  sum- 
mer than  in  winter;  in  warm  climates  than  in  cold;  in  lower  altitudes  than 
in  higher;  and  "greatest  near  the  ground  where  decomposition  is  taking 
place." 


368  entomology 

Movement 

The  movement  of  air  is  physiologically  important  in  affecting  the 
rate  of  evaporation  from  the  bodies  of  animals.  With  other  conditions 
constant,  the  rate  of  evaporation  is  proportional  to  the  strength  of 
the  air-current. 

The  directive  effect  of  currents  of  air  (anemotropism)  has  been  dis- 
cussed (page  305).  Some  insects  turn  away  from  currents  of  air  be- 
cause of  increased  evaporation.     (Shelford.) 

Winds  are  highly  effective  agents  in  the  distribution  of  insects. 
To  what  has  been  said  on  this  subject  (page  323)  these  remarks  may  be 
added. 

In  the  case  of  the  cotton  boll  weevil,  "prevaihng  winds  frequently 
cause  the  majority  of  the  insects  to  follow  one  course."  (Hunter  and 
Pierce.) 

The  natural  spread  of  the  gipsy  moth  is  accomplished  chiefly  by 
means  of  winds,  acting  on  the  hairy  first-stage  larvae.     (A.  F.  Burgess.) 

Hessian  flies  are  often  carried  two  miles,  in  an  uninjured  condition, 
by  strong  winds.  One  female  must  have  been  carried  five  miles.  (J.  W. 
McColloch.)  These  flies  may  be  borne  by  winds  with  a  velocity  of 
twenty-five  miles  or  more  per  hour;  mosquitoes,  on  the  other  hand, 
cling  to  herbage  near  the  ground  during  strong  winds,  but  are  conveyed 
many  miles  by  gentle  breezes. 

The  green-bug,  Toxoptera  graminum,  and  many  other  plant  lice 
are  widely  distributed,  as  winged  viviparous  females,  by  the  wind. 
"If  the  temperature  be  below  the  point  of  activity  for  the  species, 
it  is  very  clear  that  the  velocity  of  the  wind  would  have  no  effect  what- 
ever upon  the  diffusion  of  the  insect.  The  conditions  necessary,  then, 
for  the  wind  to  exert  its  greatest  influence  will  be  a  decreasing  food 
supply  for  the  insect  under  a  temperature  considerably  above  that 
actually  necessary  for  its  activity,  with  numbers  not  seriously  reduced 
by  parasites;  under  these  conditions,  many  species  of  aphids  are  known 
to  be  carried  about  in  immense  numbers  by  the  winds."  (Webster  and 
Phillips.) 

Electricity 

Electric  currents  have  a  directive  effect  on  animals  {electrotropism, 
galvanotropism)  but  the  conditions  under  which  this  effect  is  obtained 
are  artificial,  and  may  or  may  not  be  paralleled  in  nature. 

Atmospheric  electricity,  the  effects  of  which  vary  with  variations 


INSECT   ECOLOGY  369 

in  Other  conditions  of  the  atmosphere  (Shelford),  doubtless  exerts 
some  influence  on  the  activities  of  insects  and  other  animals,  but  in 
regard  to  this  subject  little  is  known. 

In  the  hterature  there  are  observations  of  the  effects  of  electrical 
storms  on  insects,  but  these  effects  are  results  of  several  influences 
operating  in  combination  (as  temperature,  moisture,  pressure,  light, 
and  wind  and  rain,  acting  mechanically) ;  and  possible  effects  of  elec- 
tricity alone  are  not  distinguishable. 

Evaporation 

Evaporation  depends  upon  air-temperature,  pressure,  relative 
humidity,  air-movement  and,  indirectly,  light.  The  amount  of  evapo- 
ration expresses  the  total  effect  of  these  factors.  The  evaporating  power 
of  the  air  is  "by  far  the  best  index  of  physical  conditions  surrounding 
animals  wholly  or  partly  exposed  to  the  atmosphere. "  (Shelford.)  The 
rate  of  evaporation  is  directly  correlated  with  temperature  and  illu- 
mination, but  most  closely  correlated  with  relative  humidity.     (Yapp.) 

In  the  experimental  study  of  evaporation  Livingston's  atmometer 
is  usually  employed.  This  consists  essentially  of  a  cup  of  porous  clay 
which  is  filled  with  water,  that  is  replaced  as  it  evaporates,  from  a 
reservoir  of  water.  The  amount  of  evaporation  is  easily  measured  by 
the  amount  of  water  necessary  to  restore  the  water  in  the  reservoir 
to  its  original  level. 

Few  precise  studies  have  been  made  upon  the  effects  of  evaporation 
on  insects,  though  many  have  been  made  with  man  and  other  warm- 
blooded animals. 

Metabolism  in  Relation  to  Evaporation. — "Metabolism  results 
in  heat,  and  the  temperatures  of  the  bodies  of  animals  both  warm  and 
cold  blooded,  is  nearly  always  higher  than  the  surrounding  medium,  at 
least  during  activity.  The  surrounding  conditions  may  be  stated  as 
usually  acting  on  metaboHsm,  etc.,  as  follows:  (a)  A  moist  cold  atmos- 
phere (very  low  evaporation)  causes  body  temperature  to  fall  more 
rapidly  than  a  dry  cold  one  at  the  same  temperature,  because  of  the  more 
rapid  conduction  of  heat.  Such  a  fall  in  temperature  decreases  metab- 
olism of  cold  blooded  animals,  and  increases  metabolism  of  warm  blooded 
animals  within  their  capacity  for  heat  regulation.  In  a  dry  cold  atmos- 
phere the  heat  loss  is  less  pronounced  because  of  the  less  rapid  conduc- 
tion of  heat,  (b)  In  a  dry  warm  atmosphere  (high  evaporation)  rapid 
evaporation  keeps  down  the  peripheral  temperature,  and  prevents  death 
from  over-heating  and  destructive  metabolism  in  cold  blooded  animals. 


370  ENTOMOLOGY 

and  makes  possible  body  temperature  regulation  and  thus  prevents 
heat  stroke  and  death  in  warm  blooded  animals.  In  a  moist  warm 
atmosphere,  death  and  heat  stroke  occur  because  of  lack  of  evaporation 
and  lack  of  peripheral  cooling  in  the  case  of  warm  blooded  animals 
even  when  the  surrounding  temperature  is  at  or  below  the  normal  body 
temperature,  (c)  Wind  movement  (which  increases  evaporation) 
increases  radiation  of  body  heat  and  of  heat  due  to  insolation.  It 
increases  evaporation  and  further  cools  the  body,  thus  within  certain 
limits  increasing  the  metabolism  of  warm  blooded  animals  and  de- 
creasing it  in  cold  blooded  animals,  (d)  Decrease  of  pressure  increases 
evaporation  and  radiation  both  of  which  lower  the  temperature  of 
animal  bodies  and  influence  metabolism. 

"Conditions  which  withdraw  water  from  organisms  (evaporation 
as  influenced  by  various  factors)  influence  irritabihty,  activity  and 
length  of  life  history.  Thus  Hennings  found  that  low  humidity  in- 
creased insect  metabolism  and  Sanderson  found  that  in  dry  air  the 
optimum  temperature  of  the  growth  of  insects  was  lower  than  in  moist 
air.  Factors  probably  operate  with  reference  to  an  optimum." 
(Shelford.) 

Professor  Headlee  raised  bean  weevils,  Bruchus  oUectus,  from  the 
eggs  at  a  constant  temperature  of  80°  F.,  but  with  various  degrees  of 
atmospheric  moisture,  from  less  than  i  per  cent,  to  approximately  100 
per  cent.  The  optimum  relative  humidity  was  found  to  lie  between 
80  and  89  per  cent.  At  89.7  and  100  fungi  developed  and  greatly  re- 
duced the  numbers  of  the  insects.  Comparatively  few  individuals 
reached  maturity  in  an  atmospheric  moisture  of  25  per  cent,  and  none 
in  one  of  less  than  i  per  cent. 

Burger,  as  reported  by  Shelford,  studied  the  water  relations  of 
the  meal  worm,  Tenebrio  molitor  when  kept  in  dry  air  and  fed  on  bran 
which  had  been  dried  at  105°  C.  He  believed  that  the  animals  were  in 
essentially  absolute  dryness.  Here  they  lived  for  weeks,  but  lost 
weight.  He  found,  however,  that  the  per  cent,  of  water  in  the  animals 
remained  practically  the  same  until  after  death  and  came  to  the  conclu- 
sion that  the  insect  larvae  could  not  use  their  food  to  produce  water  and 
so  the  living  substance  itself  was  used.  No  doubt  the  food  taken  pro- 
duced water  but  this  was  not  sufficient  in  quantity.  The  most  important 
fact  brought  out  was  that  the  per  cent,  of  water  remained  about  the 
same  in  spite  of  the  extreme  dryness  and  rapid  loss  of  moisture. 

Reactions." — Professor  Shelford,  who  studied  experimentally  the 
behavior  of  various  animals  under  different  rates  of  evaporation,  found 


INSECT   ECOLOGY  37 I 

that  in  dry  air  (evaporation  0.06  cc.  per  hour)  running  beetles  of  the 
genus  Pterostichus  were  very  sensitive,  exhibiting  a  preference  for 
moist  air.  Digger  wasps,  Microhemhex,  were  sHghtly  positive  to  dry 
air,  their  chief  reaction  being  digging,  which  took  place  in  medium  and 
moist  air  but  not  in  the  dry.  A  tiger  beetle,  Cicindela,  gave  a  nega- 
tive reaction  to  air  evaporating  3.6  cc.  per  hour,  and  a  positive  reaction 
to  air  evaporating  1.56  cc.  per  hour. 

Shelford  studied  also  the  influence  of  rapidly  flowing  and  of  warm 
air  in  increasing  evaporation.  All  the  animals  that  he  studied  could  be 
killed  by  loss  of  water,  when  other  conditions  remained  favorable  to 
their  existence.  The  smaller  animals  died  from  loss  of  water  much 
more  quickly  than  the  larger,  the  surface  being  greater  in  proportion  to 
the  volume  in  the  smaller  animals.  The  animals  died  after  a  smaller 
amount  of  evaporation  when  the  rate  was  slow  than  when  it  was  more 
rapid.  The  most  remarkable  fact  brought  out  was  that  the  animals  died 
more  quickly  from  evaporation  due  to  rapid  movement  of  air  than  due 
to  dryness. 

With  a  total  evaporation  of  31.0  cc.  in  a  dry  atmosphere  Pterostichus 
died  in  twenty-two  hours. 

The  Pterostichus  referred  to  came  from  under  leaves  on  the  ground 
in  a  dense  forest — a  moist  habitat;  and  Microhemhex  is  a  resident  of 
dry  open  sand  areas.  ' 

Hatching. — With  fertile  eggs  of  plant  lice  {Aphis  avence  and  A. 
pomi)  air  of  high  moisture  content  is  more  favorable  to  hatching  than 
air  having  a  lower  moisture  content.  The  moisture  content  of  the  air 
influences  the  evaporation  from  the  eggs,  determines  the  percentage  of 
hatching,  and  probably  influences  the  rate  of  splitting  of  the  outer 
layer  of  the  egg  shell.     (A.  Peterson.) 

Nymphs  of  walking-sticks,  Phasmidae,  frequently  fail  to  extract 
themselves  from  the  egg  shell,  owing  to  dryness  at  the  time  of  hatching. 
Most  of  them  succeed  in  escaping,  however,  if  supplied  with  moisture. 
In  this  instance  evaporation  has  the  mechanical  effect  of  causing  the 
appendages  or  the  abdomen  to  adhere  to  the  amniotic  membrane.  (H. 
P.  and  H.  C.  Severin.) 

Life  Cycle. — The  length  of  the  life  cycle  is  often  influenced  greatly 
by  evaporation  as  determined  by  temperature  and  relative  humidity. 
With  the  Hessian  fly,  high  temperature  and  low  humidity  lengthen  the 
cycle.  In  a  dry  atmosphere  the  eggs  shrivel;  in  periods  of  drought 
most  of  the  puparia  dry  out  and  die.  High  temperature  with  high 
humidity,  however,  does  not  retard  the  development,  and  is  not  fatal. 


372  ENTOMOLOGY 

Low  temperatures  lengthen  the  cycle  and  may  be  fatal  to  prepupal 
stages.  Low  humidity  also  increases  the  length  of  the  cycle,  and  if 
extreme  is  fatal  in  all  stages  of  development.     (Headlee.) 

Eclosion. — Every  one  who  has  had  experience  in  raising  moths 
from  pupse  knows  that  the  pupae  must  have  a  certain  amount  of 
moisture  or  they  will  dry  out  and  die.  Out  of  doors  the  rainfall  sup- 
plies the  requisite  moisture,  but  even  there  pupae  may  succumb  to  too 
much  or  too  little  moisture. 

Moths  and  butterflies  upon  emerging  from  the  pupa  can  not  expand 
their  wings  if  the  air  is  too  dry,  on  account  of  the  rapid  evaporation  of 
moisture  from  the  wings.  Indoors  the  moisture  must  be  supplied  if 
necessary.  It  has  often  been  observed  that  moths  emerge  from  cocoons 
in  greater  numbers  on  damp  days.  In  dry  weather  many  insects  emerge 
at  night,  when  the  relative  humidity  is  higher  than  in  the  daytime. 
This  incidentally  protects  the  helpless. insect  from  its  diurnal  enemies. 

Adaptations. — Many  thin-skinned  larvae,  as  those  of  the  house  fly 
and  the  plum  curculio,  that  live  in  a  moist  environment  of  decaying 
substance,  die  quickly  if  subjected  to  a  dry  atmosphere,  when  the  tem- 
perature alone  is  not  sufificiently  high  to  kill  them.  On  the  other  hand, 
larvae  with  a  thick  integument,  like  the  meal  worm,  resist  evaporation 
more  successfully. 

An  immense  number  of  dipterous  larvae,  those  of  the  Hessian  fly 
and  the  house  fly,  for  example,  when  full  grown  retain  the  larval  skin 
instead  of  shedding  it;  this  skin  drying  and  hardening  to  form  a  pupa- 
rium,  which  retards  evaporation  from  the  developing  pupa  within.  An 
unusually  hot  dry  summer  will,  however,  kill  most  of  the  puparia  of 
the  Hessian  fly,  excepting  such  as  may  be  protected  by  their  depth  in 
the  soil. 

Some  of  our  large  silkworms  smear  the  inner  surface  of  the  cocoon 
with  a  waterproof  gum  or  varnish  which  undoubtedly  prevents  the  un- 
due esca;pe  of  water  from  the  enclosed  pupa. 

Larvae  that  burrow  into  the  ground  (for  example  many  caterpillars 
and  maggots,  white  grubs,  larvae  of  the  plum  curculio,  Colorado  potato 
beetle,  and  numerous  others)  and  make  earthen  cells  in  which  to  pupate, 
secure  thereby  protection  from  evaporation  as  well  as  from  other 
influences.  Larvae  of  the  late  fall  brood  of  the  bollworm  (corn  ear 
worm)  dig  much  deeper  than  those  pupating  earlier  in  the  season. 
(Quaintance  and  Brues.) 

The  beetles  of  the  subfamily  Eleodinae  (Tenebrionidae)  that  are 
characteristic  of  arid  and  semi-arid  regions,  have  a  thick  integument  and 


INSECT   ECOLOGY  373 

are  quite  at  home  in  the  desert.  The  integument  is  possibly  no  thicker 
than  in  other  tenebrionids,  but  having  a  thick  skin  to  begin  with,  these 
forms  have  found  a  suitable  environment  and  have  thrived  in  arid 
places. 

3.  Food  Relations 

As  regards  its  kind  and  quantity,  food  is,  needless  to  say,  a  most 
important  condition  of  existence.  Examples  of  food  habits  have  been 
given  (page  212);  here  should  be  mentioned  some  of  the  more  essential 
facts  concerning  food  as  an  ecological  factor. 

Classification  of  Food  Habits. — According  to  the  nature  of  their 
food,  most  insects  may  be  classified  as  follows:  pantophagous  (omnivo- 
rous); phytophagous  (plant-eating,  referring  usually  to  the  flowering 
plants);  monophagous  (with  a  single  food  plant);  oligophagous  (with 
several  definitely  fixed  food  plants) ;  polyphagous  (feeding  indiscrimi- 
nately on  many  plants);  sarcophagous  (carnivorous);  har pacta phagous 
(predatory) ;  entomophagous  (parasitic  on  insects) ;  saprophagous  (feed- 
ing on  decaying  substances) ;  necrophagous  (feeding  on  dead  animals) ; 
coprophagous  (eating  excrementitious  material) ;  mycetophagous  (feeding 
on  fungi) ;  microphagous  (on  micro-organisms,  as  bacteria,  yeasts,  etc.) . 

Not  all  these  categories  will  be  considered  here,  but  a  few  of  them 
need  special  mention. 

Microphaga. — The  pomace  flies  (Drosophila)  famous  as  subjects  of 
investigation  by  geneticists,  feed  naturally  in  fermenting  fruits,  where 
they  find  nourishment,  not  in  the  products  of  fermentation,  but  chiefly 
in  the  yeasts  that  cause  the  fermentation.  On  sterilized  glucose-agar 
the  larvae  cannot  grow  unless  yeast  is  added;  and  a  medium  of  yeast 
nucleo-protein,  sugars  and  inorganic  salts  is  a  complete  food  for  this 
insect.     (Loeb  and  Northrop,  Baumberger.) 

Sarcophaga. — Dipterous  larvae  that  normally  feed  on  decaying 
animal  tissue  were  raised  from  eggs  to  adults  on  a  diet  of  banana  and 
yeast-agar,  by  Baumberger,  who  says  that  we  must  consider  the 
probabiUty  that  all  decaying  or  fermenting  substrata  are  merely  the 
media  on  which  fungous  or  bacterial  food  of  insects  is  growing. 

Coprophaga. — ^Larvae  of  the  house  fly  were  raised  on  bran  mash 
containing  a  heavy  growth  of  molds.  Sections  through  these  larvae 
showed  a  complete  absence  of  all  material  except  bacteria,  fungous 
spores,  and  yeast  cells  in  the  digestive  tract.  It  appears  probable  that 
the  larvae  feed  on  micro-organisms,  and  are  associated  with  them  in  the 
same  manner  as  that  of  Drosophila  and  yeasts.     (Baumberger.) 


374  ENTOMOLOGY 

Mycetophaga. — Many,  though  not  all,  of  the  fungus  flies  (Myceto- 
philidae)  feed  on  fungi.  Larvae  of  a  species  of  Sciara  that  feeds  in  woody 
tissue  were  found  to  contain  in  the  digestive  tract  fungous  mycelia 
along  with  considerable  woody  material.  Larvae  of  the  same  species 
were  reared  on  a  medium  of  bran-agar,  which  they  soon  infected  with 
molds,  upon  which  they  were  subsequently  observed  to  feed.  The 
wood  is  merely  the  substratum  in  which  the  food  material  develops. 
(Baumberger.) 

The  ambrosia  beetles,  of  which  there  are  many  species,  make  their 
tunnels  in  damp  wood  of  weak  or  dead  trees.  Their  food  is  not  wood, 
however,  but  a  fungous  growth  which  develops  rapidly  on  the  walls  of 
the  galleries — so  rapidly  often  as  to  choke  the  galleries  and  kill  their 
inmates.  The  fungus  begins  its  growth  on  a  bed  of  chips  which  the 
female  prepares,  and  on  which  she  lays  eggs.  The  fresh  tender  growth 
of  the  fungus  is  food  for  both  larvae  and  beetles,  but  only  the  latter  can 
eat  the  older  growth.  "Different  species  of  fungi  are  associated  with 
different  species  of  beetles,  and  these  associations  are  constant  for  the 
same  species  in  spite  of  changes  of  host  plants."     (Baumberger.) 

In  connection  with  this  subject  the  elaborate  fungus-gardens  of 
leaf-cutting  ants  and  of  termites  should  be  recalled  (page  295). 

Selection  of  Food. — Insects  find  food  for  themselves  or  for  their 
future  larvae  by  means  of  the  senses  of  (i)  smell,  the  most  widespread 
method;  (2)  taste,  as  with  butterflies,  pomace  flies,  flesh  flies  and  other 
forms  that  feed  as  adults;  (3)  vision,  as  with  dragon  flies,  which  after 
capturing  their  prey  test  it,  however,  and  reject  portions  unsuitable  as 
food;  also  bees,  which  can  discriminate  between  flowers  of  different 
colors. 

Brues  adds,  in  his  paper  on  this  subject,  that  the  selection  of  food 
plants  by  Lepidoptera  depends  also  on  (i)  "Some  attribute  of  the  plant, 
perhaps  an  odor  but  far  less  pronounced  to  our  own  senses  than  those 
mentioned  above.  Species  restricted  to  plants  like  Leguminosae  or 
Violaceae  may  be  considered  in  this  category.  Undoubtedly  there  is 
some  attribute  of  such  plants  which  insects  can  recognize  in  a  general 
way  and  not  as  a  specific  characteristic  of  some  single  plant  species  or 
genus.  (2)  A  similarity  in  the  immediate  environment  or  general  form 
of  the  food  plant.  The  effect  of  something  of  this  sort  is  seen  particu- 
larly in  oligophagous  and  also  polyphagous  caterpillars  feeding  mainly 
on  trees  or  shrubs,  such  as  the  gipsy  moth,  Cecropia  moth,  etc.,  and  those 
of  certain  species  like  some  of  the  Arctiid  moths  that  feed  upon  a  great 
variety  of  low  plants.     (3)  Apparently  chance  associations  that  have 


INSECT   ECOLOGY  375 

become  fixed,  whereby  diverse  plants  are  utilized  by  oligophagous 
species." 

The  selection  of  food  by  means  of  its  odor  is  simply  a  case  of  positive 
chemotropism  (see  page  302),  a  blind  reaction  to  a  chemical  substance. 
Pomace  flies,  which  feed  on  and  lay  their  eggs  in  fermenting  fruits,  are 
positively  chemotropic  to  weak  percentages  of  certain  alcohols  and 
acetic  acid,  which  are  products  of  fermentation.  House  flies  are  stimu- 
lated to  oviposition  by  ammonium  carbonate,  with  its  odor  like  that  of 
manure.  The  cabbage  butterfly  is  induced  to  lay  eggs  by  mustard 
oils,  which  occur  naturally  in  its  usual  food  plants,  Cruciferae. 

Growth. — Other  things  equal,  the  length  of  the  larval  stage  depends 
upon  the  kind,  condition,  and  amount  of  food.  With  the  house  fly,  it 
is  primarily  temperature  and  moisture  that  determine  the  rate  of  devel- 
opment; but  with  an  average  temperature  of  about  21°  C,  the  maggots 
develop  in.  horse  manure  in  fourteen  to  twenty  days,  and  on  a  diet  of 
bananas,  in  twenty-seven  days.  At  the  same  temperature,  the  rate  of 
development  is  directly  proportional  to  the  condition  of  the  food  as 
regards  moisture.  Dry  conditions  may  retard  development  five  or  six 
weeks,  tend  to  produce  flies  of  subnormal  size,  or  may  be  fatal.  (C.  G. 
Hewitt.) 

If  the  mother  insect  lays  her  eggs  in  a  considerable  supply  of  food 
substance,  as  happens  usually  in  the  case  of  the  house  fly,  pomace  fly, 
carrion  beetles,  dung  beetles,  and  many  other  insects,  the  development 
of  the  larva  is  assured,  so  far  as  the  amount  of  food  is  concerned.  The 
quantity  of  food  present  becomes  important,  however,  for  insects  that 
are  restricted  to  one  kind  of  food  plant,  or  to  a  food  of  low  nutritive 
value.  The  nutritive  content  of  wood  is  small,  and  wood-boring  cater- 
pillars and  grubs  frequently  require  long  periods  for  their  growth,  even 
several  years  (Cerambycid^) ;  though  less  time  is  needed  if  the  larvae, 
like  those  of  the  peach  tree  borers  and  the  flat-headed  apple  borer, 
feed  largely  on  the  inner  bark,  which  is  more  nutritive  than  the 
wood. 

Size. — Under-nourished  larvae  produce  small  adults,  as  might  be 
expected.  The  size  of  boll  weevils  depends  upon  the  abundance  of  the 
food  supply  and  also  upon  the  nature  of  the  food.  The  smallest  weevils 
develop  from  squares  which  are  very  small,  and  which  fall  very  soon 
after  the  egg  is  deposited ;  the  largest,  from  bolls  which  grow  to  maturity. 
In  bolls  the  food  supply  is  most  abundant,  and  the  period  of  larval 
development  is  several  times  as  long  as  it  is  in  squares.  (Hunter  and 
Pierce.) 


376  ENTOMOLOGY 

Reproduction.^ — It  goes  without  saying  that  constant  feeding  is 
necessary  in  the  case  of  long-Uved  proHfic  females,  such  as  queen  bees, 
ants,  or  termites. 

With  plant  lice,  it  has  long  been  known  that  the  drying  up  of  the 
food  plant  causes  the  appearance  of  large  numbers  of  winged,  or  migrant 
females.  In  experiments  with  the  pea  louse,  Macrosiphum  pisi,  it 
was  found  that  the  subjection  of  parthenogenetic  (reproducing  without 
fertilization)  females  to  periods  of  partial  starvation  induced  the  produc- 
tion of  winged  offspring  from  the  wingless  mothers.  These  winged 
young  would  otherwise  have  been  wingless,  as  check  experiments 
showed.     (L.  H.  Gregory.) 

In  regard  to  the  relation  of  food  to  the  production  of  the  males  and 
oviparous  (egg-laying)  females  of  plant  lice,  not  much  seems  to  be 
definitely  known. 

Fecundity. — The  kind  and  amount  of  food  influence  fecundity.  If 
female  boll  weevils  are  fed  on  leaves  alone,  eggs  do  not  develop;  while 
a  diet  of  squares  leads  to  the  development  of  eggs  in  about  four  days. 
More  eggs  are  laid  when  squares  are  abundant  than  when  they  are  few. 
(Hunter  and  Pierce.) 

Guyenot  found  that  pomace  flies  {Drosophila)  reared  from  aseptic 
larvae  on  sterile  potato  (without  yeast)  did  not  produce  offspring.  The 
flies  themselves,  if  fed  on  potato  alone,  were  much  less  prolific  than  when 
fed  on  potato  and  yeast. 

Oviposition. — With  many  adult  insects  feeding  is  not  necessary  for 
oviposition;  in  fact  the  mouth  parts  are  often  rudimentary,  as  in  some 
of  the  moths.  Such  insects  owe  their  activity  to  the  presence  of  a 
supply  of  food  stored  up  by  the  larva.  Other  insects,  however,  must 
feed  in  order  to  lay. eggs;  the  queen  honey  bee,  for  example. 

Adults  of  Pteromalus  puparum,  a  parasite  of  the  cabbage  butterfly, 
Pieris  rapee,  if  kept  without  food  for  three  days,  attempt  to  oviposit 
but  are  physically  unable  to  do  so.  If  then  fed,  however,  with  honey- 
water  or  with  blood  from  punctured  chrysalides  (their  natural  food), 
they  succeed  in  drilling  into  the  chrysalides  of  their  hosts.  When 
supplied  with  fresh  pupae  one  of  these  females  may  feed  and  lay  eggs 
for  three  weeks;  and  if  given  honey-water  also,  for  two  months. 
(S.  B.  Doten.) 

Sex-determination.— One  of  the  most  plausible  of  the  theories  of 
sex-determination  has  been  that  high  nutrition  produces  females  and  low 
nutrition,  males.  In  raising  moths  or  butterflies  from  caterpillars 
males  and  females  occur  in  about  equal  numbers,  as  a  rule.     If,  however. 


INSECT   ECOLOGY  377 

the  caterpillars  are  almost  starved,  some  will  die,  and  there  will  result 
many  more  male  adults  than  female.  Dr.  C.  V.  Riley  explained  this 
long  ago,  by  pointing  out  the  fact  that  female  caterpillars  require  a 
longer  time  for  growth  than  males  (having  sometimes  one  more  molt 
than  the  males);  so  that  conditions  of  starvation  would  kill  chiefly 
female  caterpillars,  that  had  not  completed  their  growth,  and  affect 
male  caterpillars  less.  T.  H.  Morgan,  in  a  discussion  of  the  subject, 
adopts  this  view,  and  points  out  the  fact  that  the  sex  of  the  caterpillar 
is  determined  before  the  egg  is  laid;  furthermore,  that  an  excess  of  food 
does  not  cause  an  excess  of  females. 

Longevity. — The  duration  of  life  is  evidently  related  to  food. 
Insects  cannot  live  long,  if  active,  without  food;  and  activity  is  corre- 
lated with  the  amount  of  food  utilized. 

Females  live  longer  than  males,  with  some  exceptions,  particularly 
if  they  have  not  laid  their  eggs,  and  frequently,  possess  an  ample  supply 
of  reserve  food  accumulated  by  the  larva,  as  in  the  case  of  many  moths, 
particularly  such  as  do  not  themselves  feed  as  adults  (silkworm  moth) . 

With  cotton  boll  weevils  after  emergence  from  hibernation,  unfed 
beetles  of  both  sexes  were  found  to  live  ten  days,  and  fed  beetles, 
twenty-five  days.     (Hinds  and  Yothers.) 

A  queen  honey  bee,  constantly  fed  with  highly  nutritious  food, 
may  live  more  than  four  years;  a  queen  ant,  fifteen  years  (one  instance). 
On  the  other  hand,  the  Hessian  fly,  which  does  not  feed  and  has 
little  reserve  nutriment,  lives  only  from  one  day  (males)  to  four  days 
(females) . 

A  remarkable  instance  of  longevity  under  starvation  conditions  is 
given  by  J.  E.  Wodsedalek.  Finding  that  larvae  of  the  common  museum 
beetle,  Trogoderma  tarsale,  would  live  a  long  time  without  food,  molting 
meanwhile  but  not  eating  the  cast  skins,  he  tested  their  longevity  by 
keeping  them  individually  in  glass  vials  without  food.  The  larvae 
gradually  decreased  in  size  to  almost  their  length  at  hatching,  but  were 
surprisingly  tenacious  of  Hfe.  Newly  hatched  larvae  that  had  never 
eaten  lived  four  months  without  food;  quarter-grown  larvae,  fourteen 
months;  half -grown  larvae,  three  years;  three-quarters-grown  larvae, 
four  years;  and  full  grown  individuals,  from  four  years  to  five  years, 
one  month  and  twenty-nine  days  (one  larva).  If  stunted  specimens 
were  given  food  they  began  to  grow  again,  and  could  again  be  reduced 
in  size  by  a  second  period  of  starvation.  By  alternate  periods  of  feasting 
and  fasting,  larvae  were  three  times  brought  to  their  maximum  size 
and  three  times  reduced  to  the  minimum  size. 


378  ENTOMOLOGY 

Hibernation. — Food  is  of  minor  importance  as  an  incentive  to  hiber- 
nation. Codling  moth  caterpillars,  woolly  bears  {Isia  isahella)  and 
many  other  insects  enter  hibernation  before  there  is  any  failure  of  the 
food  supply. 

Insects  which  feed  on  evergreen  trees  are  not  as  rhythmical  in 
their  hibernation  as  those  which  feed  on  deciduous  trees.  (Pictet, 
Baumberger.) 

Some  larvae  are  full-fed  upon  entering  hibernation  (codHng  moth) ; 
while  others  are  not  (brown- tail  moth).  Emergence  from  hibernation 
depends  immediately  upon  temperature,  but  it  is  possible  that  hunger 
also  is  a  stimulus  to  the  renewal  of  activity. 

As  metabolism  is  at  its  minimum  in  hibernating  insects,  their  food 
requirement  is  similarly  small. 

Coloration. — Food,  as  regards  kind  and  condition,  often  affects 
coloration,  particularly  pigmental  coloration  (see  page  176). 

In  the  cotton  boll  weevil  the  color  becomes  darker  with  age;  conse- 
quently, hibernated  individuals  are  the  darkest  found;  but  food  also 
influences  the  color.  The  smaller  the  size  of  the  weevil,  the  darker 
brown  is  its  color;  the  largest  weevils  are  light  yellowish  brown.  The 
principal  reason  for  the  variation,  in  the  opinion  of  Dr.  W.  E.  Hinds, 
lies  in  the  degree  of  development  of  the  minute,  hair-like  scales,  which 
are  much  more  prominently  developed  in  the  large  than  in  the  small 
specimens,  although  the  color  of  old  specimens  is  often  changed  by, the 
abrasion  of  the  scales.  These  scales  are  yellow  in  color,  while  the  ground 
color  of  the  integument  bearing  them  is  a  dark  brown  or  reddish  brown. 
The  development  of  the  scales  appears  to  take  place  mostly  after  the 
adult  weevils  have  become  quite  dark  in  color,  but  before  the  chitin 
becomes  fully  hardened.  They  seem,  therefore,  to  be,  to  a  certain 
extent,  an  aftergrowth  which  depends  upon  the  surplus  food  supply 
remaining  after  the  development  of  the  essential  parts  of  the  weevil 
structure.     (Hunter  and  Pierce.) 

Food  Relations  in  General. — A  phytophagous  species  which  is 
limited  to  one  species  of  food  plant  frequently  dies  out  in  a  locality 
from  having  consumed  or  fatally  weakened  all  its  food  plants  (the  but- 
terfly L.  philenor,  on  Aristolochia,  in  the  North). 

Evidently,  a  species  which  has  many  kinds  of  food  plants  has  an 
advantage  (gipsy  moth,  grasshoppers,  army  worm,  etc.). 

The  quantity  of  food  present  becomes  important  for  an  insect  that 
is  restricted  to  a  single  species  of  plant.     It  may  be  a  plant  that  is 


INSECT   ECOLOGY  379 

always  abundant,  like  the  pawpaw,  to  which  the  Ajax  butterfly  is 
confined;  or  it  may  not  be. 

In  a  state  of  nature,  if  food  plants  of  one  species  are  scattered  among 
other  plants,  their  insect  enemies  do  not  become  injurious;  but  in  a 
state  of  nature,  if  many  plants  of  one  species  grow  together,  insects  may 
injure  them  (in  forests,  for  example).  Where  man  grows  one  kind  of 
plant  over  a  large  area,  insect  enemies  flourish  (Hessian  fly,  chinch  bug, 
cotton  boll  weevil,  codling  moth,  etc.). 

The  same  relations  exist  between  parasites  or  predators  and  their 
hosts.  A  parasitic  species  of  insect  that  is  limited  to  one  species  of  host 
will  die  if  it  destroys  all  the  individuals  of  the  host  species.  The 
successful  parasites  (as  Ichneumonidae,  Chalcididae,  and  Braconidai) 
are  those  that  have  available  immense  numbers  of  a  single  species  of 
host,  or  a  large  number  of  species  as  hosts. 

Most  predaceous  insects,  however,  feed  indifferently  on  almost  any 
species  of  insects  that  they  can  overcome,  and  of  ten  do  not  limit  them- 
selves to  insects  for  food;  therefore  their  numbers  are  not  affected  by  the 
absence  of  this  or  that  species  of  possible  victim. 

These  food  relations  form  a  most  important  factor  in  the  interactions 
of  organisms,  the  subject  next  to  be  considered. 

4.  BiOTic  Conditions 

The  animals  and  plants  of  a  region  form  a  vast  complex,  in  which 
every  organism  affects  every  other,  directly  or  indirectly,  and  is  in  turn 
affected  by  all  the  others.  Furthermore,  all  the  organisms  are  influenced 
by  their  environment,  and  in  turn  affect  the  character  of  the  environ- 
ment itself  more  or  less.  All  the  organisms  are  bound  up  with  one 
another  in  an  intricate  network  of  interactions  which  the  mind  can  only 
partially  comprehend. 

Interactions. — As  a  familiar  illustration  of  these  interactions,  take 
the  case  of  any  common  plant  louse  and  the  extensive  society,  or  conso- 
cies,  which  it  dominates. 

To  begin  with,  the  numbers  of  aphids  depend  greatly  upon  inorganic 
influences,  as  heat  or  cold,  dryness  or  moisture;  evaporation  being 
important.  Aphids  are  often  blown  off  their  plants,  or  washed  off  by 
rains,  and  killed  mechanically.  When  they  are  abundant,  many  are 
squeezed  to  death  between  branches  that  are  blown  against  each  other. 
Bacteria  and  fungi  destroy  the  lice.  The  fungus,  Empusa  aphidis,  is 
the  most  important  enemy,  for  in  damp  weather  it  can  almost  extermi- 


38o 


ENTOMOLOGY 


nate  plant  lice  locally.  Weather  conditions  may  render  the  plants 
unfit  for  food,  or  may  prevent  the  eggs  from  hatching.  In  short, 
aphids  are  affected  for  good  or  ill  by  all  the  influences  that  act  upon 
their  food  plants. 

Enemies  are  abundant.  Many  kinds  of  spiders  and  a  few  kinds  of 
mites  kill  the  Hce.  The  EngHsh  sparrow  eats  the  pea  louse  voraciously, 
and  the  chickadee  in  winter  consumes  enormous  numbers  of  aphid  eggs. 
Most  of  the  enemies  are,  however,  other  insects.  Here  are  lists  of  the 
insects  known  to  affect,  directly  or  indirectly,  the  common  pea  louse, 
or  clover  louse,  Macrosiphum  pisi. 


Predators^ 


CoccinellidcR  (lady  beetles) 
Ceratomegilla  fuscilabris 
Hippodamia  tredecimpunctata 
Hippodamia  parenthesis 
Hippodamia  glacialis 
Hippodamia  convergens 
Coccinella  novemnotata 
Cycloneda  sanguinea 
Adalia  bipunctata 
Chilocorus  bivulnerus 

SyrphidcB  (flower  flies) 

Ocyptamus  fuscipennis 
Platychirus  quadratus 
Syrphus  americanus 
Syrphus  ribesii 
Allograpta  obliqua 
Mesogramma  marginata 
Mesogramma  polita 
Sphaerophoria  cylindrica 


ChrysopidcB  (lace-wings) 
Chrysopa  oculata 
Chrysopa  rufilabris 
Chrysopa  plorabunda 

Gryllida  (tree-crickets) 
(Ecanthus  confluens 

Pentalomidce  (stink  bugs) 
Podisus  maculiventris 
Euschistus  variolarius 

Anthocoridce.  (flower  bugs) 
Triphleps  insidiosus 

CantharidcB  (cantharids) 
Podabrus  rugulosus 
Podabrus  tomentosus 

Ilonididce  (gall  gnats) 

Aphidoletes  meridionalis 


IchneumonidcB  (ichneumons) 
Praon  simulans 
Trioxys  cerasaphis 
Aphidius  fletcheri 


Parasites 


Aphidius  washingtonensis 

Aphidius  rosse 
Miscogasteridce  (miscogasterids) 

Megorismus  fletcheri 


The  species  of  the  preceding  list  feed  directly  on  the  pea  louse. 
Those  of  the  following  list  affect  the  louse  indirectly,  by  feeding  on  the 
preceding  species  or  on  one  another. 


1  Additional   details  in  regard  to  all  these  insects  will  be  found  in  Bull.  111.  Agr.  Exp. 
Sta.,  No.  134,  and  Bull.  U.  S.  Dept.  Agr.,  No.  276. 


INSECT   ECOLOGY  38 I 

Affecting  M.  pisi  Indirectly 
Braconida  (braconids) 

Perilitiis  americanus,  parasitic  on  the  beetles,  Ceralomegilla  fuscilahris  and   Coccinella 
novemnotata. 

Bassus  Icetotorius,  a  parasite  bred  from  larvjc  and  pupa;  of  Allograpla  obliqua  and  five 
other  species  of  Syrphidce. 
Figitidce  (figitids) 

Sohnaspis  hyalinus,  a  parasite  from  larvae  of  M esogramma  polila. 
Pteromalidcc  (pteromalids) 

Pachynenron  syrphi,  a  parasite  of  Bassus  Icetotorius. 
EncyrtidcB  (encyrtids) 

Encyrlus  mesograptcB,  a  parasite  from  larvae  of  M esogramma  polita. 
Chalcididce  (chalcids) 

Isocratus  vulgaris,  a  parasite  of  Bassus  Icetotorius. 
Proctotry pidce  (proctotrypids) 

Telenomus  podisi,  a  parasite  of  the  eggs  of  Podisus  and  Euschislus. 

A  few  examples  will  illustrate  the  intricacy  of  the  interrelations  of 
these  insects  that  are  dominated  by  Macrosiphum  pisi. 

M.  pisi  is  preyed  upon  by  lady  beetles,  the  pupae  of  which  are  sucked 
by  the  stink  bugs,  the  eggs  of  which  are  parasitized  by  a  proctotrypid. 

M.  pisi  is  food  for  larvae  of  flower  flies,  the  larvae  and  pupae  of  which 
are  parasitized  by  a  braconid,  which  is  itself  parasitized  by  a  pteromahd 
and  a  chalcid. 

M.  pisi  is  destroyed  by  larvae  of  flower  flies,  the  larvae  of  which  are 
attacked  by  stink  bugs,  while  the  adults  are  eaten  by  robber  flies,  toads, 
and  various  birds,  as  the  kingbird,  flicker  andphoebe. 

Thus  forty  species  of  insects  are  known  to  be  vitally  concerned  with 
the  pea  louse.  There  should  be  added  the  mite,  Rhyncholophus  parvus, 
which  feeds  on  the  louse. 

The  writer  has  found  more  than  two  hundred  species  of  insects  in  a 
field  of  red  clover.  All  these  have  some  influence  on  the  pea  louse 
(clover  louse)  and  on  each  other;  though  the  influence  is  often  remote  in 
its  effects  and  practically  insignificant.  The  scavenger  insects  on  the 
ground,  and  collembolans  etc.,  in  the  soil,  feeding  on  organic  matter, 
affect  the  texture  and  composition  of  the  soil  and  consequently  the 
plant.  Without  considering  earthworms,  moles,  mice,  birds  and  many 
other  animal  factors  that  might  be  thought  of,  we  shall  mention  insects 
orfly.  The  bees  that  pollenize  the  flowers,  and  the  various  insects  that 
destroy  the  roots,  stems,  leaves  or  flowers,  all  affect  indirectly  the  louse. 
As  illustrating  interactions,  though  it  is  of  no  practical  consequence, 
we  may  say  that  the  yield  of  clover  seed  depends  slightly  upon  the  struc- 
ture of  the  milkweed  flower;  for  flower  flies  whose  larvae  destroy  plant 


382  ENTOMOLOGY 

lice  are  sometimes  fatally  entangled  in  the  flowers  of  milkweed.  We 
might  even  go  farther,  and  implicate  all  the  factors  that  control  milk- 
weed; and  so  on  indefinitely.  Such  speculation  is  not  altogether  profit- 
less, if  one  bears  in  mind  the  fact  that  only  the  more  immediate 
influences  are  of  any  practical  importance,  and  that  the  effect  of  one 
factor  may  be  increased,  diminished,  or  neutralized  by  that  of  another. 

Every  one  of  the  insects  or  other  animals  that  affect  the  clover 
louse  directly  or  indirectly,  is  itself  the  center  of  a  little  world  of  inter- 
actions. Though  we  cannot  follow  all  these  interactions,  their  total 
effect  at  any  given  time  is  expressed  by  the  existing  number  of  individ- 
uals of  each  of  the  species  involved;  which  measures  also  the  success  of 
each  species  from  its  own  point  of  view,  so  to  speak. 

Equilibrium.— It  is  not  surprising,  then,  that  species  fluctuate  in  num- 
ber of  individuals.  The  presence  or  absence,  or  increase  or  decrease, 
of  one  influence  may  affect  many  other  factors,  and  disturb  preexist- 
ing relations.  This  is  seen  in  the  case  of  the  rapid  multiplication  of 
the  gipsy  moth  and  the  San  Jose  scale  insect,  when  introduced  into 
this  country  without  their  natural  enemies. 

Evidently  there  is  actually  no  such  thing  as  a  "balance  of  nature," 
a  true  equilibrium;  on  the  contrary  there  is  continual  fluctuation 
within  wider  or  narrower  limits.  The  so-called  equilibrium  is  simply 
a  condition  of  relatively  small  fluctuation.  Under  conditions  of 
nature,  animals  and  plants  approximate  a  condition  of  stability,  or 
fluctuation  within  comparatively  narrow  limits,  to  the  benefit  of  all 
concerned.  Under  artificial  conditions,  however,  as  when  man  grows 
one  kind  of  plant  over  a  large  area,  the  insects  of  the  plant  multiply 
rapidly.  Man  is  able  to  remedy  such  disturbances  of  the  "order  of 
nature"  in  proportion  to  his  knowledge  of  the  factors  concerned,  espe- 
cially of  their  relative  importance.  He  has  unwisely  introduced  the 
English  sparrow  to  subdue  caterpillars;  but  has  wisely  imported  and 
propagated  the  native  enemies  of  the  fluted  scale,  the  gipsy  moth,  and 
other  pests. 

II.  Conditions  or  Aquatic  Existence 

The  fundamental  physiological  requirements  are  the  same  for 
aquatic  as  for  terrestrial  animals,  but  these  conditions  are  often  met  in 
different  ways  in  the  two  groups.  Though  insects  may  broadly  be 
divided  into  these  two  groups,  there  are  many  kinds  whose  environment 
is  intermediate  between  water  and  land,  and  many  forms  are  aquatic 
in  their  immature  stages  and  terrestrial  as  adults. 


INSECT   ECOLOGY  383 

I.  Chemical  Conditions 

Animals  cannot  exist  in  water  that  does  not  contain  certain 
gases  and  chemical  compounds  in  solution. 

Gases. — Oxygen  is  a  necessity,  and  most  aquatic  animals  select 
water  with  a  high  oxygen  content.  In  air  dissolved  in  water  the  pro- 
portion of  oxygen  to  nitrogen  is  much  larger  than  it  is  in  atmospheric 
air ;  because  oxygen  is  more  soluble  in  water  than  nitrogen.  The  oxygen 
content  of  the  water  is  more  variable  than  that  of  the  atmosphere. 
The  importance  of  the  oxygen  factor  is  indicated  by  the  many  elaborate 
adaptations  for  respiration  displayed  by  aquatic  insects. 

Carbon  dioxide  given  off  by  animals  during  respiration,  acts  in 
small  quantities  as  a  stimulation  to  respiration,  and  in  large  amounts 
as  a  narcotic  capable  of  fatal  effects.  Aquatic  animals  react  nega- 
tively to  even  a  small  increase  of  carbon  dioxide.  This  is  due  to  the 
increase  in  hydrogen-ion  concentration  which  it  causes.  Since  a  large 
amount  of  dissolved  carbon  dioxide  is  commonly  accompanied  by  a 
low  oxygen  content  as  well  as  other  important  factors,  the  hydrogen-ion 
concentration  of  waters  of  low  alkalinity  is  probably  the  best  single 
index  of  the  suitability  of  the  water  for  animals.     (Shelf ord.) 

"Nitrogen  has  little  effect  upon  animals  except  when  present  in 
excess."     (Shelford.) 

"Oxygen  and  nitrogen  go  into  solution  from  the  atmosphere  and 
oxygen  is  also  produced  by  green  plants.  The  other  gases  are  produced 
chiefly  by  organisms  as  excretory  and  decomposition  products." 
(Shelford.) 

Chemical  Compounds.^ — Carbonates,  sulphates,  and  chlorides  of 
magnesium,  calcium,  and  sodium,  and  salts  of  potassium,  iron,  and 
silicon  are  practically  always  present  in  solution  in  water,  and  their 
presence  in  definite  proportions  is  essential  to  the  life  of  the  animals. 
(Shelford.)  Sodium  chloride,  or  common  salt,  is  unfavorable  to  insect 
life.  Almost  no  insects  live  in  the  ocean  (see  p.  170).  In  fact,  if  an 
insect  larva  be  taken  from  a  brook  and  put  in  a  brackish  pool  it  will 
actually  lose  water  through  its  skin ;  it  will  partly  dry  up.  (F.  E.  Lutz.) 
Flies  of  the  genus  Ephydra  are,  however  exceptional  in  this  respect. 
Two  species  of  these  "salt-flies"  are  abundant  in  Great  Salt  Lake,  the 
salinity  of  which  is  greater  than  that  of  the  ocean.  The  flies  and  pupa- 
ria  sometimes  occur  in  inconceivable  numbers,  the  latter  forming  large 
brown  patches  on  the  water  or  windrows  on  the  shore.  The  larvae, 
which  feed  on  an  alga,  are  active  even  when  the  water  evaporates 


384  ENTOMOLOGY  ^ 

down  until  covered  with  a  crust  of  salt.  (J.  M.  Aldrich.)  Not  a  few 
insects  live  in  brackish  water,  however;  some  of  them  occurring  also 
in  fresh  water;  as  the  nymphs  of  certain  dragon  flies,  which  inhabit  also 
salt,  sulphurous,  or  slightly  alkaline  ponds  in  the  West.  (R.  C.  Osburn.) 
A  few  Hemiptera  of  fresh- water  occur  also  in  brackish  water  or  in  water 
strongly  impregnated  with  various  mineral  salts.  (H.  G.  Barber.) 
Several  species  of  mosquitoes  confine  themselves  for  breeding  purposes 
to  salt  marshes,  where  A'edes  sollicitans  is  always  the  most  abundant 
and  is  found  in  practically  all  the  temporary  pools  uninhabited  by  fish. 
(J.  A.  Grossbeck.) 

Larvae  of  the  malaria  mosquitoes  {Anopheles)  also  develop  in 
brackish  water.  The  salt  marsh  mosquito  {Aedes  sollicitans)  was 
found  to  develop  in  water  so  strongly  polluted  with  acid  waste  from  a 
"guano  factory"  that  all  other  animal  life  appeared  to  be  extinct. 
(S.  F.  Hildebrand.) 

Water  containing  certain  acids,  as  the  humic  acids  of  peat  bogs,  is 
deleterious  to  insect  life. 

.2.  Physical  Conditions 

Circtilation. — "The  distribution  of  dissolved  salts  and  gases  is 
dependent  upon  the  circulation  of  the  water,  as  their  diffusion  is  too 
slow  to  keep  them  evenly  distributed.  The  circulation  of  water  in 
streams  is  probably  such  as  to  keep  all  dissolved  gases  and  salts  about 
equally  distributed.  The  water  of  streams  has  been  found  to  be 
supersaturated  with  oxygen.  Oxygen  is  taken  up  by  the  water  near  the 
surface.  Nitrogen  and  carbon  dioxide  are  produced  especially  near  the 
bottom,  and  if  the  water  did  not  circulate  they  would  be  too  abundant 
in  some  places  and  deficient  in  others  for  animals  to  Uve. "     (Shelf ord.) 

The  flowing  or  splashing  of  water  increases  the  oxygen  content. 
Larvae  such  as  the  hellgrammite,  those  of  black-flies  (Simulium)  and 
of  some  caddis  flies  (as  Hydropsyche)  require  well-aerated  water,  and 
are  found  always  in  moving  water,  often  in  strong  currents.  They 
occur  in  flowing  water  not  primarily  on  account  of  its  greater  oxygen 
content,  however,  but  because,  as  Shelford  has  shown,  such  animals 
orient  themselves  toward  a  strong  current  of  water  (positive  rheotaxis) 
and  move  against  the  current.  Furthermore,  they  are  positively  thig- 
motactic  and  show  a  strong  preference  for  hard  surfaces,  as  those  of 
large  stones;  with  an  avoidance  of  sand;  the  members  of  a  rapids 
community  differing  from  those  of  a  pool  community  in  this  respect. 


INSECT   ECOLOGY  385 

Hydropsyche  reacts  positively  to  the  direction  of  light,  though  indifferent 
to  its  intensity;  but  some  other  members  of  the  rapids  community,  as 
hellgrammites  and  burrowing  caddis  worms,  avoid  light. 

"Current  is  an  important  factor  of  aquatic  environments  which 
finds  its  terrestrial  counterpart  in  winds.  That  it  is  a  very  important 
factor  is  shown  by  the  numerous  devices  aquatic  insects  have  to  keep 
their  position,  and  it  varies  from  nothing  in  puddles  to  the  rush  of 
Niagara."  (F.E.Lutz.)  Larvae  of  the  black-flies  are  fastened  to  stones 
or  other  objects;  some  caddis  worms  anchor  their  cases  securely;  beetles 
of  the  family  Elmidae  cling  with  their  claws  tightly  to  submerged  objects. 
With  caddis  flies  of  the  family  Hydropsychidae,  which  live  in  swift 
streams,  the  instantaneous  emergence  of  the  adult  as  soon  as  the  pupa 
reaches  the  surface  prevents  the  fly  from  being  swept  away.  (C.  E. 
Sleight.) 

Temperature. — Temperature  is  of  great  indirect  importance  in  the 
control  of  the  distribution  of  life  in  water.  (Shelford.)  It  is  "more 
constant  in  aquatic  environments  than  in  terrestrial,  although  it  is 
somewhat  variable  from  place  to  place  and  month  to  month.  In  the 
summer,  a  spring  hole  is  cooler  than  a  rainwater  puddle  and  the  opposite 
is  apt  to  be  true  in  the  winter.  In  general,  a  running  stream  is  apt  to 
be  cooler  in  summer  than  a  stagnant  one.  In  the  spring  a  deep  pond  is 
generally  cooler  than  a  shallow  one,  and  the  opposite  is  true  in  the 
autumn.  But  aquatic  insects  are  never  subject  to  the  sharp  daily 
fluctuations  of  temperature  that  most  of  their  terrestrial  relatives  must 
bear,  and  even  the  annual  range  of  temperature  variations  is  slight. " 
(F.  E.  Lutz.)  Such  differences  as  there  are  have,  however,  an  influence 
on  aquatic  life.  Temperature  affects  activities  of  various  kinds,  as 
locomotion  and  oviposition;  may  determine  the  length  of  the  egg- 
period;  or  may  act  in  other  ways. 

Light. — Light  controls  distribution  and  activities.  Its  intensity 
decreases  rapidly,  particularly  that  of  the  orange  and  red  rays,  with  the 
depth  of  the  water.  Aquatic  insects,  like  terrestrial,  react  either  posi- 
tively or  negatively  to  the  directive  action  of  light  {phototropism,  p. 
306).  Some  of  them  frequent  shaded  or  dark  places,  while  others,  as 
the  whirHgig-beetles  {Gyrinidce)  and  the  water-striders  {Gerrida)  are 
at  home  on  the  surface  of  the  water  in  the  strongest  sunlight. 

Pressure. — Pressure  in  water  increases  with  depth,  at  the  rate  of 
about  one  atmosphere  for  each  thirty-three  feet  (Shelford) .  Its  effects 
on  aquatic  insects  are  for  the  most  part  indirect;  the  pressure  affecting 
other  conditions  of  existence. 

25 


386  ENTOMOLOGY 

Depth. — Depth  is  mostly  important  indirectly,  on  account  of  its 
influence  on  other  conditions,  such  as  circulation,  temperature,  light, 
and  pressure;  but  is  in  itself  a  determining  condition  in  some  instances. 
Thus  such  larvae  of  horse-flies  (Tabanidae)  as  have  a  posterior  res- 
piratory tube  bearing  the  spiracles  must  have  shallow  water,  where  the 
spiracles  can  be  raised  to  the  surface;  though  sometimes  these  larvae 
are  found  in  moist  earth  where  there  is  no  standing  water.  (R.  C. 
Osburn.) 

Bottom. — "The  character  of  materials  and  topography  of  the 
bottom  are  very  important  to  animals  living  on  the  bottom,  but  it  has 
its  effect  also  on  free  swimming  animals  as  a  determining  factor  in  the 
amount  of  sediment.  The  kind  of  bottom  is  important  because  many 
animals  are  dependent  upon  sohd  objects  for  attachment  and  are  absent 
from  bottoms  made  up  of  fine  materials.  Others  must  burrow  into 
mud  or  creep  on  sand  and  gravel. "     (Shelford.) 

Most  Dytiscidae  prefer  clean  live  water,  being  averse  to  very  muddy 
bottoms.  (J.  D.  Sherman.)  On  the  other  hand,  nymphs  of  various  dra- 
gon flies  bury  themselves  in  the  mud.  Some  of  the  caddis  worms  prefer 
a  clear  sandy  bottom;  others,  a  bottom  with  slime,  or  one  with  sticks, 
dead  leaves  or  other  debris. 

Vegetation. — It  goes  without  saying  that  vegetation,  in  its  amount 
and  kind,  is  extremely  important  as  a  condition  of  aquatic  existence. 
The  green  plants  give  off  oxygen.  Plants  are  used  for  shelter,  escape 
from  enemies,  as  places  in  which  to  wait  for  the  prey  (dragon  fly 
nymphs,  Zaitha),  as  surfaces  for  locomotion  (non-swimming  larvae 
of  diving  beetles,  whirligig  beetles  and  others) ,  especially  as  a  means  of 
reaching  the  surface  for  air  or  for  the  transformation  (dragonfly  nymphs, 
etc.).  Eggs  may  be  laid  on  the  plants  (electric  light  bugs,  back-swim- 
mers. May  flies,  caddis  flies,  etc.)  or  inserted  into  plant  tissues  (diving 
beetles,  water  scorpions). 

3.  Food  Conditions 

The  small  beetles  of  the  family  HalipHdae  are  said  to  feed  on  algae. 
The  water-scavenger  beetles  (Hydrophilidae)  feed  mostly  on  decaying 
vegetable  matter,  but  are  sometimes  carnivorous,  and  some  ofjthe 
adults  will  eat  green  vegetation.  The  diving  beetles  (Dytiscidae) 
are  carnivorous;  the  whirhgig  beetles  (Gyrinidae)  feed  on  small  insects 
found  on  the  surface  of  the  water.  The  water-striders  (Gerridae) 
capture  disabled  or  living  insects  for  food;  the  water  boatmen  (Corix- 


INSECT   ECOLOGY  387 

idae)  are  predaceous.  Nymphs  of  dragon  flies  are  predaceous,  catching 
other  insects  by  means  of  their  peculiar  extensile  lower  lip,  and  even 
young  fishes,  tadpoles  and  smaller  nymphs  of  their  own  kind.  (R.  C. 
Osburn.)  Most  caddis  worms  are  plant-eating,  but  some  are  insectiv- 
orous, as  Hydropsyche,  which  catches  its  victims  in  the  nets  that  it 
spreads  in  swift  currents.  May  fly  nymphs  are  carnivorous,  or  feed  on 
plants  or  mud.     Additional  examples  of  food  habits  are  given  on  p.  165. 

4.  BiOTic  Conditions 

Aquatic  animals  and  plants,  like  terrestrial,  form  a  vast  complex  of 
organisms  that  interact  upon  one  another  in  innumerable  ways  and  are 
acted  upon  by  the  environment;  but  the  interactions  are  different  to  the 
extent  that  the  aquatic  environment  differs  from  the  terrestrial.  As 
a  whole,  the  physical  and  chemical  conditions  of  existence  are  more 
uniform  in  water  th^n  on  land.  Furthermore,  the  number  of  species 
concerned  is  fewer;  thus  aquatic  insects  form  only  3  per  cent,  of  all 
insects.  As  regards  food  supply,  the  truism  that  its  diminution  lessens 
the  numbers  of  the  animals  dependent  upon  it,  applies  of  course,  as  with 
terrestrial  forms.  Aquatic  insects  are,  however,  much  less  specialized 
than  terrestrial  as  regards  food  habits.  Thus  the  plant-eating  species 
are  seldom  limited  to  one  species  of  plant,  therefore  can  always  find 
food,  even  though  there  are  fewer  species  of  aquatic  plants  than  of 
terrestrial.  The  great  majority  of  aquatic  insects  are,  however,  carniv- 
orous, and  many  are  omnivorous,  and  rarely  suffer  from  lack  of  food. 
Though  the  predaceous  habit  is  highly  developed  among  aquatic 
insects,  the  parasitic  habit  has  developed  almost  entirely  among  terres- 
trial forms;  and  aquatic  insects,  while  actually  in  the  water,  are  practi- 
cally free  from  the  attacks  of  parasitic  insects. 

On  the  whole,  the  interrelations  of  aquatic  forms,  though  incon- 
ceivably complex,  are  less  extensive  than  those  of  terrestrial  species. 

The  so-called  equilibrium  or  "balance  of  nature"  is  maintained,, 
which  is,  as  on  land,  a  condition  of  continual  fluctuation  within  rela- 
tively narrow  limits;  with  a  smaller  range  of  fluctuation  in  the  aquatic 
environment. 

Ill .  Environmental  Factors  in  General 

The  important  factors  of  the  environment  have  been  considered 
individually.     In  nature  they  do  not  operate  singly,  however,  and  by 


388  ENTOMOLOGY 

simple  observation,  unaided  by  experimentation,  one  cannot  disen- 
tangle the  effects  of  one  factor  from  those  of  others  acting  with  it. 
The  environment  is  a  complex  of  many  interdependent  factors. 

The  factors  control  one  another,  but  those  that  are  more  immediate 
in  their  operation  are  controlled  by  the  larger  influences  of  physiography 
and  vegetation. 

Physiography .^ — "In  streams,  current  and  oxygen  content  are 
determined  very  largely  by  physiographic  conditions.  Current  is  a 
function  of  volume  of  water  and  slope  of  stream  bed.  Oxygen  content 
is  largely  determined  by  the  rate  of  flow,  and  therefore  is  influenced  by 
physiography.  In  lakes,  oxygen  content  is  determined  by  the  depth, 
the  temperature,  and  winds — physiographic  factors  are  again  important. 
On  land,  moisture  and  light  are  in  a  measure  controlled  by  physio- 
graphic features.  Slope  and  direction  of  facing  profoundly  affect 
vegetation,  moisture,  and  light."     (Shelford.) 

Siirface  Materials  and  Vegetation.^"  Materials  for  abode  are 
largely  the  surface  soil  or  rock  or  the  vegetation.  Surface  soil  or  rock 
influences  the  moisture.  Both  moisture  and  surface  materials  influ- 
ence the  kind  and  amount  of  vegetation.     All  are  interdependent. 

"Physiographic  features  change  with  time.  Erosion  changes  the 
gradient  of  streams,  the  width  of  valleys,  the  steepness  of  valley  walls 
and  cliffs,  the  ground- water  level,  etc.  The  weathering  of  rock  is  a 
process  familiar  to  all.  It  is  the  aggregate  of  processes  by  which  the 
coarse'  and  hard  or  massive  materials  are  reduced  to  clay  and  soil. 
This  requires  time. 

"The  fact  that  vegetation  grows  upon  the  so-called  sterile,  coarse, 
rough-surface  materials,  usually  scattered  or  ephemeral  at  first,  but 
increasing  in  denseness  with  each  generation,  is  also  familiar.  Plants 
add  organic  matter  to  the  soil.  This  organic  matter  holds  the  water 
so  that  moisture  increases  and  plants  may  increase.  With  such  changes 
it  is  obvious  that  an  area  of  sterile  soil  will  support  more  animals  as 
time  goes  on,  than  at  the  outset,  when  the  conditions  were  such  that 
only  a  few  hardy  species  could  live.  Here  again,  then,  time  is  the 
important  factor  in  determining  the  change  of  the  area,  so  as  to  be 
suitable  for  more  species  (because  more  species  are  adapted  to  live  in 
the  resulting  than  in  the  initial  conditions) .  The  length  of  time  which 
has  elapsed  since  a  given  set  of  surface  and  physiographic  conditions 
became  exposed  to  the  atmosphere  is  very  important  in  governing  the 
number,  kind,  and  distribution  of  animals  in  a  given  area."     (Shelford.) 


INSECT   ECOLOGY  389 

IV.  Classification  of  Environments 

The  distinction  must  be  made  between  climatic  environmental 
complexes  and  local  complexes.  "The  climate,  and  such  features  as 
types  of  vegetation  covering  large  areas,  e.g.,  steppe,  deciduous  forest, 
etc.,  are  commonly  regarded  as  climatic.  Opposed  to  these,  and  lying 
within  them,  are  the  local  conditions,  such  as  streams,  lakes,  soils, 
exposure,  etc.,  which  are  only  indirectly  dependent  upon  climate." 
(Shelford.) 

The  classification  of  animal  environments  is  based  upon  vegetation, 
physiography,  or  both.  Where  vegetation  exists,  animal  communities 
are  referred  to  the  plant  communities  which  form  their  environments. 
(Plate  V.) 

The  simple  and  natural  classification  of  plant  communities  recom- 
mended by  Livingston  and  Shreve  is  illustrated  as  follows: 

"The  extensive  areas  such  as  the  sagebrush  plains  of  the  Great 
Basin,  the  grasslands  of  Nebraska  and  Kansas,  or  the  pine  forests  of 
the  Atlantic  Coastal  Plain  are  designated  sls  formations .  The  smaller 
and  less  markedly  differentiated  areas  within  a  formation  are  designated 
as  associations,  as,  for  example,  the  forests  of  shortleaf  pine  in  New 
Jersey,  those  of  loblolly  pine  in  Maryland  and  Virginia,  and  those  of 
longleaf  pine  in  the  Gulf  States,  all  lying  within  the  Coastal  Plain 
formation.  The  smallest  units  of  vegetation  are  [sometimes]  termed 
societies,  and  these  are  of  small  area  and  represent  portions  of  the  associa- 
tion in  which  a  definite  aggregation  of  species  is  to  be  found."  (Living- 
ston and  Shreve.) 

An  outline  of  the  content  of  animal  ecology  prepared  by  a  committee 
of  the  Ecological  Society  of  America,  in  1920,  contains  the  following 
useful  synopsis. 

Distribution  of  Communities 
I.  Land  communities. 

(a)  Forests  with  broad  thin  leaves. 

1.  Continuously  moist  and  evergreen. 

(a)  Uniformly  warm,  affording  habitats  in  six  or  more  strata.     (Tropical 

rain  forests.) 
(6)  With  cool  season.     (Temperate  rain  forests.) 

2.  Intermittently  dry  or  cold,  and  deciduous. 

(a)  Warm  with  distinct  dry  season.     (Tropical  deciduous  forest.) 

(b)  With  cold  winter,  little  winter  shelter.     (Temperate  deciduous  forest.) 

(b)  Communities  of  evergreen  forests  of  narrow,  thick  leaves. 

1.  Moist  conifer  forest  with  little  undergrowth. 

2.  Rainy  conifer  forest  with  shrub  undergrowth. 
5.  Open,  arid,  conifer  forest. 


390  ENTOMOLOGY 

(c)  Communities  of  sav^anna  and  grassland. 

1.  Tropical  savanna  (dry  season)  affording  habitats  in  groves,  thickets,  forest 

margins  and  grasslands. 

2.  Tropical  steppe;  large  herds  of  mammals. 

3.  Temperate   savanna;   habitats   in   groves,    thickets,    forest   margins    and 

grasslands. 

4.  Temperate  steppe  with  cold  or  dry  winters  and  usually  large    herds  of 

mammals. 

5.  Arid,  broken,  bush-covered  steppe  with  small  herds  of  mammals. 

((f)  Communities  of  winter  rain  (forests  with  broad  thick  leaves)    e.g.,  California 

semi-desert, 
(e)  Communities  of  desert  and  semi-desert. 

1.  Grass,  cactus,  tree  semi-desert  with  grazing  mammals  (e.g.,  South  Texas 

semi-desert);  succulent  semi-desert;  shrub-covered  semi-desert. 

2.  Extreme  desert  without  large  diurnal  mammals. 
(/)  Arctic  and  Alpine  lands. 

1.  Tundra. 

2.  Alpine  meadows.  / 

3.  Ice  fields. 

2.  Communities  of  waters  and  shores. 

(a)  Communities  of  the  sea  (Marine). 

1.  Communities  of  the  open  sea  (Pelagic). 

(a)  Mid-oceanic  communities. 

(b)  Oceanic  island  communities. 

(c)  Sargassum  communities. 

(d)  Coastal  oceanic  communities. 

2.  Communities  of  the  sea  bottom  (Benthic). 

3.  Littoral  communities. 

(a)  Communities  of  eroding  shores;  subdivisions  based  on  exposure, 
bottom  material  and  latitude. 

(fi)  Communities  of  depositing  shores;  subdivisions  as  above  plus  vegeta- 
tion. 

(c)  Special  communities:  coral;  tidepools;  kelp. 

3.  Communities  of  the  sea  shores.     Animals  feeding  in  the  sea  and  breeding  on  the  land, 

or  vice  versa.     Classification  based  on  climate. 

4.  Communities  of  the  fresh  waters. 

(c)  Communities  of  still  waters.     Subdivisions  based  on  size,  depth  and  vegetation; 
littoral,  pelagic,  benthic. 

(b)  Communities    of    turbulent  waters.     Sbdivisions   based  on  character   of  water 
movement. 

(c)  Swamps,  marshes,  etc. 


Ecology  finds  its  distinctive  field  of  study  in  communities  and 
succession.  These  important  subjects  can  not,  however,  be  adequately 
presented  from  an  entomological  viewpoint  alone.  Furthermore,  little 
has  been  published  on  the  subject  as  regards  insects.  The  most  that 
can  be  done  here  is  to  illustrate  the  subject  by  naming  some  of  the  better 
known  insects  as  being  characteristic  of  a  few  typical  environments, 
and  to  add  occasional  remarks  on  adaptation  in  relation  to  habitat. 


Plate  V. 


€01  Bli 


INSECT   ECOLOGY  395 

V.  Communities 

In  a  given  habitat  the  fauna  and  flora  together  constitute  a  biota. 
The  term  fauna  is  generally  used  in  connection  with  classification  or 
geographical  distribution,  as  is  also  the  term  flora.  In  reference  to 
ecological  relations,  however,  the  animals  or  plants  of  a  given  habitat 
constitute  a  community. 

As  animals  and  plants,  according  to  their  structural  resemblances  or 
differences,  fall  into  species,  genera,  families,  orders,  etc.,  so  do  animal 
or  plant  communities,  according  to  their  ecological  likenesses  or  unlike- 
nesses,  fall  into  mores,  consocies,  strata,  associations,  and  formations; 
each  of  these  orders  being  inclusive  of  the  preceding  kind;  there  the 
resemblance  ends.  The  animals  of  a  community  agree  in  their  reactions 
to  the  factors  that  they  encounter.  If  they  meet  environmental  influ- 
ences in  the  same  way,  they  are  said  to  be  ecologically  similar;  if  they 
meet  the  same  influences  in  different  ways,  they  are  ecologically  equiva- 
lent. Thus  a  caterpillar  that  meets  low  temperature  by  making  a  co- 
coon, and  one  that  gets  the  same  result  by  digging  into  the  ground, 
are  ecologically  equivalent.  Animals  select  their  habitats,  probably  by 
trial  and  error;  and  their  behavior  becomes  adjusted  to  the  surrounding 
conditions.  (Shelf  ord.)  ' '  The  habitat  is  the  mold  into  which  the  organ- 
ism fits.  Since  habitats  are  different,  animal  communities  occupying 
different  habitats  are  physiologically  different.  Communities  are  sys- 
tems of  correlated  working  parts."     (Shelford.) 

''Mores  are  groups  of  organisms  in  full  agreement  as  to  physiological 
life  histories  as  shown  by  the  details  of  habitat  preference,  time  of 
reproduction,  reactions  to  physical  factors  of  the  environments,  etc. 
The  organisms  constituting  a  mores  usually  belong  to  a  single  species 
but  may  include  more  than  one  species. 

"Consocies  are  groups  of  mores  usually  dominated  by  one  or  two  of 
the  mores  concerned  and  in  agreement  as  to  the  main  features  of  habitat 
preference,  reaction  to  physical  factors,  time  of  reproduction,  etc. 
Example:  the  prairie  aphid  consocies.  The  aphids  dominate  a  group  of 
organisms  which  for  the  most  part  prey  upon  them,  as,  for  instance, 
certain  species  of  lacewing,  lady  beetles,  syrphus-flies,  etc. 

"Strata  are  groups  of  consocies  (and  animals  not  so  grouped)  occupy- 
ing the  recognizable  vertical  divisions  of  a  uniform  area.  Strata  are  in 
agreement  as  to  material  for  abode  and  general  physical  conditions  but 
in  less  detail  than  the  consocies  which  constitute  them. 

"For  example,  a  forest-animal  community  is  clearly  divisible  into 


394  ENTOMOLOGY 

the  subterranean-ground  stratum,  the  field  stratum  (zone  of  the  tops 
of  the  herbaceous  vegetation),  the  shrub  stratum  (zone  of  the  tops  of 
the  dominant  shrubs),  the  /ou'erZ/'gestratum  (zone  of  the  shaded  branches 
of  the  trees),  and  the  upper  tree  stratum.  A  given  animal  is  classified 
primarily  with  the  stratum  in  which  it  breeds,  as  being  most  impor- 
tant to  it,  and  secondarily  with  the  stratum  in  which  it  feeds,  etc.,  as  in 
many  cases  most  important  to  other  animals.  The  migration  of  ani- 
mals from  one  stratum  to  another  makes  the  division  lines  difficult  to 
draw  in  some  cases.  Still,  the  recognition  of  strata  is  essential  but  a 
rigid  classification  undesirable.  Consocies  boring  into  the  wood  of 
living  trees  probably  should  be  considered  as  consocies  relatively 
independent  of  stratification  phenomena. 

^^Associations  are  groups  of  strata  uniform  over  a  considerable  area. 
The  majority  of  mores,  consocies,  and  strata  are  different  in  different 
associations.  A  minority  of  strata  may  be  similar.  The  term  is 
applied  in  particular  to  stages  of  formation  development  of  this  ranking. 
The  unity  of  associations  is  dependent  upon  the  migration  of  the 
same  individual  and  the  same  mores  from  one  stratum  to  another  at 
different  times  of  day  or  at  different  periods  of  their  life  histories. 
Migration  is  far  more  frequent  from  stratum  to  stratum  than  from  one 
association  to  another. 

"Formations  are  groups  of  physiologically  similar  associations. 
Formations  differ  from  one  another  in  all  strata,  no  two  being  closely 
similar.  The  number  of  species  common  to  two  formations  is  usually 
small  (e.g.,  5  per  cent.).  Migrations  of  individuals  from  one  formation 
to  another  are  relatively  rare."     (Shelford.) 

VI.  Examples  of  Insect  Communities 

The  article  by  A.  G.  Vestal,  from  which  the  following  extracts  are 
taken,  though  limited  to  a  single  group  of  insects,  the  grasshoppers, 
is  a  good  example  of  how  entomological  field  observations  may  be 
organized  on  an  ecological  basis.  The  observations  were  made  at 
Douglas  Lake.  Michigan. 

Community-relations  of  Grasshoppers 

Northeastern  Conifer  Formation.— r//w/a  Association. — Cedar  and 
peat  bog.     Melanoplus  islandicus  the  only  species. 

Aspen  Association. — In  treeless  parts,  M.  angustipennis  is  the 
common  species.     M.  luridus  is  found  sparingly  in  scattered  aspen 


INSECT   ECOLOGY  395 

growths.  Scirtetica  marmorata  occurs  usually  on  or  near  the  hchen- 
covered  surfaces. 

Eastern  Deciduous  Forest  Formation. — Herbaceous  Associations. — 
Hot  dry  clearings.  Grasshoppers  are  numerous  both  in  individuals  and 
in  species.  In  order  of  abundance:  Melanoplus  atlanis,  Camnula 
pellucida,  Dissosteira  Carolina  (Carolina  locust),  etc. 

Thicket  and  Bramble  Associations. — :M.  bivittatus  occasional  on 
shrubs.     M.  atlanis  and  others  occur  on  the  ground. 

Local  Associations. — Dry  Beach. — Pure  sand,  dry  and  shifting, 
with  full  exposure  to  sun  and  wind.  Here  are  several  species  of  grass- 
hoppers, which  occur  also  in  other  habitats.  Trimerotropis  maritima 
(the  seaside  grasshopper,  p.  196)  is,  however,  limited  to  this  habitat, 
and  has  the  same  brownish  color  as  the  sand. 

Marsh  Associations. — Several  species  of  grasshoppers  are  found  in 
the  tall,  rather  close,  sedge  or  grass  growths.  Stenobothris  curtipennis 
is  the  characteristic  grasshopper  of  littoral  situations. 

Ruderal  Associations. — Dry  Grassland. — Waste  places,  dry  pastures, 
abandoned  fields,  roadsides,  etc.  In  order  of  importance:  M.  atlanis, 
Camnula  pellucida,  M.  bivittatus,  Dissosteira  Carolina,  Arphia  pseudo- 
nietana.  All  these  species,  with  the  possible  exception  of  the  last,  are 
more  abundant  in  ruderal  than  in  native  vegetation. 

Sparsely  Vegetated  or  Bare  Soil. — The  CEdipodinae  normally  rest  on 
bare  soil  and  oviposit  in  it.  Bare  soil  as  a  habitat  is,  however,  not 
sufficient;  nearby  vegetation  is  necessary.  Grasshoppers  are  rare  on 
extensive  areas  of  bare  soil,  except  at  the  borders.  They  are  conspicu- 
ous on  bare  places,  but  are  more  abundant  in  the  interspaces  between 
plants,  in  open  growths.  The  Carolina  locust,  Dissosteira  Carolina,  is 
the  most  familiar  species  of  bare  soil,  though  other  species  have  the 
same  habitat. 

Meadow  Associations. — Variable  in  character.  In  a  bluegrass- white 
clover  meadow,  M.  atlanis  and  Stenobothris  curtipennis  are  of  about  equal 
abundance.  The  red-legged  locust,  M .  femur-rubrum  is  more  abundant 
than  these  in  such  places,  in  some  localities.  The  differential  locust, 
M.  dijferentialis ,  is  typical  in  meadow  habitats. 

1.  Grasshoppers  are  more  abundant,  in  species  and  in  individuals, 
in  herbaceous  or  grassland  habitats  than  in  forest,  and  more  abundant 
in  dry  than  in  moist  or  wet  situations. 

2.  Certain  species  are  much  more  restricted  than  others  in  range  of 
habitats,  and  in  accompanying  range  of  toleration  of  physical  and 
vegetational  factors  of  the  environment. 


396  ENTOMOLOGY 

3.  Although  a  species  may  be  found  over  several  associations,  it  is 
more  abundant  in  one,  or  two,  of  these,  than  in  others.  Certain  activi- 
ties take  place  in  more  restricted  habitats;  chief  of  these  restricted 
activities  is  the  laying  of  eggs. 

4.  No  two  plant  associations  have  identical  grasshopper  assemblages. 

5.  No  two  grasshopper  species  have  identical  habitat-preferences. 
It  should  be  said  that  these  scanty  excerpts  give  no  idea  of  the  scope 

of  Vestal's  article;  most  important  in  which  are  the  ecological  generaliza- 
tions. 

Mr.  A.  P.  Morse,  authority  on  Orthoptera,  has  paid  particular  atten- 
tion to  the  subjects  of  distribution  and  adaptation.  His  data  were  given 
according  to  life  zones  and  habitats,  but  are  rearranged  here  as  follows. 

Shores  of  Seas  and  Lakes. — Bare  sands,  hot  and  dry.  Ground 
Stratum.  The  seaside  locust,  Trimerotropis  maritima,  found  along  the 
Atlantic  coast  from  Maine  to  North  Carolina,  and  inland  about  the 
Great  Lakes,  is  a  characteristic  arenicolous  (sand-dwelling)  species, 
which  varies  in  color  from  gray  to  brown,  in  harmony  with  its  local 
habitat  (see  p.  196). 

Salt  Marshes  and  Vegetation  Bordering  Brackish  Waters. — Moist 
Soil.  Ground  and  Herbaceous  Strata.  Orphulella  olivacea,  occurring 
along  the  Atlantic  coast  from  Connecticut  to  Florida  and  Texas;  the 
only  halophilous  (inhabiting  salty  soil)  locust  of  the  Eastern  States. 

Semi-Arid  Areas. — Hot  and  Dry.  Herbaceous  and  Shrub  Strata. 
Eesperotettix  pratensis,  ranging  from  Mexico  and  Texas  to  Washington, 
and  California  to  Indiana;  occurring  also  in  the  Southeastern  States  a- 
mid  conditions  much  resembling  those  of  its  habitats  in  the  arid  West; 
for  example  along  the  Gulf  shore  of  Florida,  among  the  xerophytic 
(inhabiting  hot,  dry  places)  strand  vegetation. 

Temperate  Savanna  and  Grassland  Formation.— Heihsiceons  Stratum. 
Orphulella  picturata  and  Melanoplus  bispinosus  are  common  on  the 
prairies  west  of  the  Mississippi.  In  damp  grassy  fields  the  red-legged 
locust,  Melanoplus  femur-rubrum,  is  common;  in  dry  grassy  fields,  M. 
atlanis.  On  ruderal  dry  grasslands  are  species  of  Arphia,  Syrbula,  etc. 
On  bare  soil,  hot  and  dry,  are  the  Carolina  locust,  Dissosteira  Carolina, 
and  Trimerotropis  citrina.  On  the  moist  banks  of  streams,  M.  femora- 
tus.  On  moist  soil  of  sandy  loam,  or  the  banks  or  beds  of  freshwater 
streams,  somewhat  exposed,  are  the  grouse  locusts,  Tetriginae,  some  of 
which  feed  sometimes  on  humus.  On  bunch-grass  in  fields  or  openings 
in  the  forest  is  Eesperotettix  brevipennis,  limited  to  this  plant. 

Temperate  Deciduous  Forest  Formation. — In  the  undergrowth  is  Mela- 


INSECT    ECOLOGY  397 

noplus  strumosus.  On  bare  or  lichen-crusted  rock  occurs  Trimerotropis 
saxatilis  (see  page  197),  which  occupied  that  station  before  the  forest 
came. 

Adaptations. — "Brachypterism  (the  short-winged  condition)  in 
locusts  is  a  more  complete  adaptation  to  a  leaping  mode  of  progression 
brought  about  by  life  in  situations  where  flight  is  difficult  or  impracti- 
cable, and  consequently  disadvantageous.  That  this  is  the  true  ex- 
planation is  indicated  by  the  habits  and  haunts  of  the  majority  of  the 
flightless  species  (sylvan  surroundings  or  tangled  undergrowth  wherever 
found);  by  their  distribution  locally,  horizontally,  and  vertically;  and 
by  the  equally  characteristic  habits,  haunts,  and  distribution  of  macrop- 
terous  (long- winged)  species  as  inhabitants  of  the  open  field,  desert,  or 
savanna. 

"The  advantages  of  progression  by  fiight^dispersal  widely  and 
easily  effected,  often  aided  by  the  wind,  ease  of  escape  from  many  ene- 
mies, etc.,  and  the  superiority  of  this  mode  in  open  lands — are  evident 
to  all.  On  the  other  hand,  long  wings  and  locomotion  by  flight  are 
disadvantageous  amid  dense  underbrush,  where  a  leaping  mode  of 
progression  has  decided  advantages.  Organs  unused  or  disadvanta- 
geous tend  to  dwindle  and  disappear;  hence  the  loss  of  wings. 

"It  is  found  that  Orthoptera  frequenting  habitats  involving  passage 
over  open  spaces  of  considerable  extent,  such  as  fields,  between  trees  in 
forests,  and  bushes  or  thickets  in  deserts,  are  usually  long-winged,  flying 
species;  and  others  dwelling  in  an  environment  of  more  or  less  dense, 
intricate,  interlacing  vegetal  growth,  be  it  sub-alpine  or  sub-tropical, 
in  forest  or  swamp — or  in  burrows,  crevices,  etc., — in  short,  in  stations 
where  wings  are  not  needed  or  are  at  a  disadvantage,  are  very  generally 
apterous  (wingless)  or  brachypterous  (short-winged). 

"Brachypterism,  therefore,  appears  to  be  largely  not  so  much  a  case 
of  natural  selection  through  the  agency  of  the  wind  as  an  adaptation  in 
structure  to  habits.  The  fact  that  the  heavier-bodied  female  is  more 
frequently  or  completely  brachypterous  than  the  male  and  that  the  teg- 
mina  in  the  latter  sex  when  used  as  musical  organs  are  retained  in  a 
less  degenerate  condition  (even  when  entirely  useless  in  flight) ,  confirms 
this  explanation  of  brachypterism."     (A.  P.  Morse.) 

Communities  of  Streams 

From  Shelf ord's  notable  volume.  Animal  Communities  in  Temperate 
North  America,  we  may  take,  from  the  wealth  of  data  given,  examples  of 
common  insects  representing  the  various  communities  of  streams. 


398  ENTOMOLOGY 

Intermittent  Stream  Communities.  Temporary  rapids  consocies. — 
The  larva  of  the  black-fly,  Siniulium,  found  in  the  smallest  trickle  of 
water.  Nymphs  of  May  flies,  as  the  stream  grows  a  little  larger.  No 
permanent  aquatic  residents,  however,  in  these  temporary  streams. 
The  temporary  residents  may  fail  to  transform  if  the  water  dries  out  too 
soon.  Temporary  pool  consocies. — -Somewhat  more  permanent.  Insects 
that  belong  primarily  to  stagnant  ponds  make  their  appearance. 
Permanent  pool  communities. — A  practically  permanent  fauna.  Water 
striders,  back-swimmers,  water  boatmen,  etc.  are  common.  Dragon  fly 
nymphs,   diving  beetles,   crane  fly  larvae,   and  many   other  insects. 

Spring  Brook  Associations. — In  streams  fed  by  springs.  On  the 
stones,  larvae  of  the  black-fly,  Simulium,  and  the  caddis  fly,  Hydropsyche. 
Under  the  stones,  nymphs  of  May  flies  and  larvae  of  flies  and  midges 
{Chironomus,  Dixa). 

Swift-stream  Commimities.  Hydropsyche  or  Rapids  Formation. — 
Three  ecologically  equivalent  modes  of  life,  each  meeting  the  current  in 
a  different  way.  These  are  (i)  clinging  to  stones  in  the  current,  (2) 
avoiding  the  current  by  creeping  under  stones,  (3)  self-maintenance  by 
strong  swimming  powers.  Upper  surface  of  stones  (stratum  i) : 
black-fly  larvae,  hanging  from  stones  to  which  they  are  attached  by 
means  of  a  sucker  at  the  posterior  end  of  the  body.  Caddis  worms, 
Hydropsyche,  in  cases  made  of  pebbles;  with  a  net  for  catching  floating 
food.  Among  the  stones  (stratum  2) :  miscellaneous  insects,  also  of  the 
following  stratum.  Under  the  stones  (stratum  3) :  May  fly  nymphs, 
larvae  of  midges,  Chironomus,  and  of  horse  flies,  Tabanus.  Stone  fly 
nymphs,  Perlidae,  with  flattened  bodies.  Larvae  of  the  parnid  beetle 
Psephenus.  Caddis  worms,  Helicopsyche.  Nymphs  of  the  damsel 
fly,  Calopteryx,  if  vegetation  is  present.  Sandy  and  gravelly  bottom  forma- 
tion (pools). — Bloodworms,  Chironomus.  The  burrowing  dragon  fly 
nymph,  Gomphus  exilis,  a  burrowing  May  fly  nymph,  caddis  worms. 

Sandy  Bottomed  Streams.- — With  shifting  bottom,  the  animals 
present  being  those  which  belong  to  moderately  swift  water.  Brook 
beetles,  Parnidae,  attached  to  the  few  scattered  plants.  On  logs  and 
roots,  many  Parnidae;  predaceous  diving  beetles,  Dytiscidae,  hiding  in 
the  crevices;  a  few  caddis  worms,  Hydropsyche;  the  little  dytiscid, 
Hydroporus  mellitus,  which  buries  itself  in  the  sand. 

Sluggish  Stream  Commimities.  Sand  and  Silt  Bottom  Formations. — 
Bloodworms,  Chironomidas ;  green  midge  larvae,  Chironomidae ;  occa- 
sional caddis  worms,  Hydropsyche;  a  burrowing  May  fly  nymph, 
Hexagenia.    Formation  of  the  Vegetation. — A  densely  rooted  vegetation. 


INSECT    ECOLOGY  399 

as  in  ponds.  Large  numbers  of  diverse  insects,  rnany  of  which  come 
to  the  surface  for  air,  both  in  the  adult  and  the  young  stages.  Water 
scorpions,  Ranatra;  creeping  water  bugs,  Pelocoris  femoratus;  small  water 
bug,  Zaitha  fluminea;  water  boatmen,  Corixa;  predaceous  diving  beetles, 
Dytiscidae;  water  scavenger  beetles,  Hydrophilida;.  The  gilled  aquatic 
insects  are  the  May  fly  nymphs,  Ccenis  and  Callihcetis;  damsel  fly 
nymphs,  Ischnura  verticalis;  diagon  fly  nymphs,  ^^schnidae  and 
Libellulidaj;  these  utilizing  the  vegetation  as  resting-places  or  clinging- 
places,  or  as  a  means  of  creeping  to  the  surface  to   transform. 

Tension  Lines. — Margins  of  bodies  of  water,  swamps  and  marshes, 
and  temporary  ponds  are  on  the  border  line  between  land  and  water. 
The  classification  of  the  communities  of  such  tension  lines  of  overlapping 
environments  is  often  diflicult.     (Shelford.) 

Along  the  margins  of  young  ponds  and  lakes  is  an  area  which  is 
characterized  by  being  made  up  of  wet  sand  or  mud  which  is  submerged 
at  high  water  and  moist  at  other  times.  Here  we  find  springtails 
(especially  Poc^wm  aquatica),  shore  bugs  (Saldidae),  many  tiger  beetles 
(Cicindelidae)  and  numerous  small  flies.  The  ground  beetle  {Bemhidion 
cannula)  and  numerous  scavengers  (Staphylinidas,  Histeridae,  etc.) 
are  common  because  the  beach  is  often  strewn  with  dead  animals  which 
have  floated  ashore.     (Shelford.) 

In  Shelf ord's  Animal  Communities  there  are  extended  accounts  of 
communities  of  streams,  lakes,  ponds,  prairies,  and  forests. 

Community  Relations  in  New   Mexico 

The  notes  that  follow  on  the  insect  ecology  of  New  Mexico  are  taken 
from  an  interesting  report  by  Professor  J.  R.  Watson.  They  are 
here  arranged  under  four  of  Livingston's  vegetational  areas. 

Northern  Mesophytic  Evergreen  Forest  Formation.  Douglas 
Spruce  Association. — Poor  in  insect  life.  Some  thirty  species  listed.  The 
carpenter  ant,  Camponotus  pennsylvanicus ,  is  common  here  and  in  the 
yellow  pine  association,  but  was  not  seen  outside  of  the  mountains. 
The  butterfly,  Grapta  zephyrus,  is  also  limited  to  these  two  associations. 
The  familiar  mourning  cloak  butterfly,  Vanessa  antiopa,  is  present. 
Yellow  Pine  Association.- — About  fifty  species  of  insects  listed.  Machi- 
lis  sp.  The  hemipteron  Oncometopia  lateralis  is  confined  to  this  asso- 
ciation. Circotettix  undulatus  is  very  rare  outside  of  this  association; 
it  makes  the  loudest  noise  of  any  grasshopper  in  the  region.  Another 
locust,  Arphia  acta,  noteworthy  for  its  loud  crackling  noise,  is  common, 
and  descends  into  the  cedar  association. 


400  ENTOMOLOGY 

Western  Xerophytic  Evergreen  Forest  Formation.— A  dwarf  and 
open  form  of  semi-forest  that  characterizes  the  edges  of  the  preceding 
formation.  Pinon  Association.- — The  locust,  Trimerotropis  cyanea,  is 
especially  at  home  here.  The  hemipteron,  Perihalus  limbolarius,  is 
very  abundant  on  blossoms  of  Yucca.  The  skipper  butterfly  Epargyreus 
tityrus  seems  to  belong  here.  Cedar  Association. — The  tarantula  killer, 
Pepsis  formosa,  is  particularly  abundant  here.  On  milkweed,  which  is 
more  abundant  here  than  elsewhere,  is  the  cerambycid  beetle,  Tetraopes 
iemoratus,  and  the  hemipteron,  LygcBUs  turcicus. 

Desert-grassland  Transition  Formation. — Intermediate  between 
the  Grasslands  to  the  east  and  the  Desert  regions  to  the  west.  Opuntia 
arborescens  Society.— Several  insect  species  are  quite  characteristic  of 
this  society.  The  nitidulid  beetle,  Carpophilus  pallipennis,  eats  the 
pollen  and  petals  of  the  Opuntia  and  every  blossom  commonly  shows 
from  a  dozen  to  a  hundred  or  more  individuals.  The  peculiar  ceram- 
bycid beetle,  Presmis  pocularis,  and  the  next  insect  are  chiefly  respon- 
sible for  weakening  and  kilHng  the  cactus  plants.  The  beetle  apparently 
never  leaves  the  plant,  and  its  wings  are  degenerate.  The  female  is 
usually  seen  carrying  her  much  smaller  mate.  The  larvae  bore  in  the  tis- 
sues of  the  plant.  The  cicada,  Cacama  valvata,  is  very  abundant  on  the 
tree  cactus,  but,  unlike  the  last,  also  occurs  on  the  prickly  pears.  The 
loud  calls  of  the  males  are  heard  on  every  hand  when  the  sun  is  shining. 
But  let  a  cloud  obscure  the  sky  for  a  moment  and  all  is  hushed.  The 
larvae  feed  on  the  roots  of  the  cactus.  Shortgrass  Association. — The  mesa 
grasshopper,  Trimerotropis  vinculata  is  extremely  numerous,  ascending 
even  into  the  yellow  pine  association.  It  is  very  variable  in  color  and 
the  variations  have  a  very  definite  relation  to  that  of  the  ground  around 
them,  being  very  light  on  sandy  soil,  mottled  on  pebbly  hills  and  darker 
among  the  pines  where  there  is  more  vegetation.  The  species  migrates 
in  large  numbers  when  the  rains  cease  and  the  grasses  on  which  it  feeds 
dry  out.  Many  species  of  insects  inhabit  the  mesa.  Here  lives  the 
harvesting  ant,  Pogonomyrmex  occidentalis  (see  page  297).  It  is  well 
known  that  these  ants  bring  their  stores  of  grain  out  to  air  occasionally. 
Professor  Watson  relates  that  "One  somewhat  windy  day  in  September, 
a  hill  was  visited  in  which  part  of  the  ants  were  busily  engaged  in 
bringing  out  the  grain  to  air  and  others  were  as  busily  engaged  in 
carrying  it  back  again.  One  ant  would  drop  a  grain  and  at  once  start 
back  without  a  load  into  the  hill  for  another,  whereupon  the  grain 
would  be  at  once  seized  by  another  ant  and  carried  back  into  the  gran- 
ary.    It  is  possible  that  this  treatment  is  what  the  grain  needed  but  it 


INSECT    ECOLOGY  4OI 

looked  to  the  interested  observer  like  a  serious  disagreement  in  the 
colony  as  to  where  that  grain  should  be,  a  case  illustrating  the  limita- 
tions of  instinct  in  developing  'team  work.'  " 

Large  centipedes,  Scolopendra,  are  quite  common,  often  entering 
houses  and  being  much  feared;  though  their  bite  is  by  no  means  as 
serious  as  represented.  The  whip-scorpion,  Thelyphonus,  "is  rarely 
met  with  on  the  mesa.  Though  probably  poisonous,  its  bite  is  also 
grossly  exaggerated  in  popular  belief. "  (Watson.)  Tarantulas,  Lycosa, 
"are  somewhat  more  common  than  the  last  but  much  less  so  than  the 
centipedes.  Their  bite  is  more  serious  than  any  of  the  above,  but  still 
not  dangerous  to  most  people."     (Watson.) 

Rio  Grande  Semi-desert  Formation. — Hot  and  dry.  Gutierrezia 
Association. — The  big  clumsy  sand-cricket,  Stenopelmalus  fasciatus, 
is  common  under  stones,  etc.  Several  species  of  the  tenebrionid  sub- 
family Eleodinae  are  characteristic.  One  of  these  beetles,  Eleodes 
longicollis,  when  held,  can  squirt  an  ill-smelling  fluid  to  a  distance  of 
eight  inches.  The  large  black  tenebrionid  beetles,  Eusattus  convexus, 
"form  a  very  large  and  characteristic  feature  of  the  fauna  of  this  region. 
They  are  true  children  of  the  desert.  Their  elytra  are  grown  together 
and  to  their  backs,  an  adaptation  to  the  fierce  sand  storms  of  the  mesa. 
These  wind  storms  drifting  sand  and  gravel  with  them  are  a  source  of 
grave  danger  to  the  fauna  of  the  region,  even  to  man  himself.  The 
author  has  several  times  been  caught  out  on  the  mesa  when  one  struck 
the  region  with  its  usual  suddenness  and  has  stopped  to  observe  the 
behavior  of  the  animals.  The  prairie  horned  larks  sought  the  shelter 
of  the  friendly  arroyo  banks.  (The  author  has  picked  up  these  birds 
on  the  mesa  during  one  of  these  storms.  They  were  so  exhausted  by  the 
buffeting  that  they  had  received  that  they  made  no  effort  to  escape.) 
The  digger  wasps  climbed  into  the  Gutierrezia  bushes  and  hung  on  for 
dear  life  with  all  of  their  feet  wrapped  about  the  stem,  an  attitude  that 
they  also  assume  during  a  shower;  the  snout  beetles  on  the  other  hand 
backed  down  off  the  Gutierrezia  and  sought  shelter  in  the  ground;  the 
woolly  bears  and  other  caterpillars  curled  up  under  the  shelter  of  tufts 
of  grass;  most  of  the  lizards  sought  their  holes  as  did  the  harvester 
ants;  but  these  Tenebrionidae  went  about  their  business  as  usual  entirely 
oblivious,  apparently,  of  the  storm.  Their  heavy  bodies  kept  them 
from  being  blown  away  and  their  heavy  coat  of  chitin  (it  is  hardly 
possible  to  force  a  heavy  insect  pin  through  some  species)  defied  the  drift- 
ing wind.  In  their  disposition  not  to  be  too  particular  as  to  what  they 
eat  they  again  show  that  they  are  true  children  of  the  desert.     Anything 


402  ENTOMOLOGY 

from  the  tender  green  seedling  leaves  of  a  Hoflfmanseggia  to  a  dead 
member  of  their  own  species  is  good.  They  collect  in  large  numbers 
about  the  carcass  of  a  dead  mammal.  They  will  come  out  from  their 
winter  quarters  under  the  rosettes  of  Yucca  and  other  sheltered  places 
any  time  in  winter  if  it  is  as  warm  as  60°  F.  They  have  been  taken  by 
the  author  on  January  15.  On  the  other  hand  they  seem  somewhat 
to  shun  the  hottest  hours  of  the  day  in  summer,  being  then  much  more 
noticeable  toward  sunset."     (J.  R.  Watson.) 

In  the  shallow  depressions  or  "draw"  in  the  mesa  above  the  place 
where  a  definite  arroyo  develops,  there  is  found  a  society  of  which 
certain  quick-growing  annual  grasses  are  most  conspicuous.  "Here 
and  here  only  have  I  ever  found  this  big,  nearly  wingless,  'lubberly 
locust '  (Brachystola  magna) ,  a  good  illustration  of  an  insect  restricted 
to  a  very  limited  habitat. "  (Watson.)  The  grasshopper,  Heliastus 
aridus,  is  particularly  abundant  in  these  arroyos,  where  its  mottled 
colors  agree  perfectly  with  the  gravelly  surface. 

Chrysothamnus  Association. — Occupying  such  rapidly  eroding  and 
hence  unstable  situations  as  the  dissected  edge  of  the  mesa  and  the 
higher  gravelly  parts  of  the  valley  of  the  Rio  Grande,  this  is  the  most 
xerophytic  (inhabiting  hot  dry  places)  of  the  associations.  The  charac- 
teristic tenebrionid  beetle,  Cysteodemus  wislizeni,  is  very  common  in 
colonies,  which  are  spread  over  much  ground.  The  ambush  bug, 
Phymata  erosa  fasciata  is  very  abundant;  it  is  almost  perfectly  concealed 
in  yellow  blossoms,  as  those  of  golden  rod,  where  it  occurs  more  com- 
monly than  in  white  blossoms.  The  clear-winged  moth,  Calesesia 
coccinea,  is  exceedingly  abundant  on  Hymenopappus  during  the  third 
week  in  May;  its  conspicuous  colors  blending  perfectly  with  those  of  the 
blossoms  of  this  plant.  The  insect  disappears  by  the  first  of  June. 
The  magnificent  noctuid  moth,  Erebus  odora,  is  occasionally  taken. 

The  sand  dunes  are  entirely  barren  of  vegetation  and  of  insect  life 
except  for  a  species  of  digger-wasp,  Bembex,  which  here  finds  conditions 
favorable  for  its  colonies.  "All  the  specimens  of  the  scorpion  {Buthus) 
that  I  have  seen  have  come  from  this  association.  Its  sting  is,  to 
most  people,  not  nearly  as  serious  as  it  is  represented  to  be.  Persons 
that  have  experienced  it  say  that  for  a  short  time  only  is  the  pain  more 
severe  than  that  resulting  from  the  sting  of  a  hornet  and  that  it  does 
not  last  as  long. "  (Watson.)  In  the  Croton  Society  the  short-winged, 
tricolored,  or  "barber-pole"  grasshopper,  Dactylotum  pictum,  occurs 
wherever  its  food  plant,  Croton  texensis,  occurs  in  sufficient  abundance. 
The  walking-stick,  Diapheromera  femorata,  is  present  also.     It  is,  of 


INSECT    ECOLOGY  403 

course,  perfectly  harmless,  but  is  charged  by  the  natives  with  causing 
the  death  of  many  a  poor  horse. 

In  the  "Valley"  insects  are  abundant  in  number  of  species  and  of 
individuals;  but  the  term  valley  does  not  signify  much,  ecologically, 
since  it  may  mean  anything  from  mud  flats  to  desert.  On  the  mesa, 
dragon  flies  range  five  or  six  miles  from  any  possible  breeding  place, 
but  the  feebler  damsel  flies  never  fly  far  from  home.  The  harlequin 
cabbage  bug  is  sometimes  abundant  on  Cleome  and  on  cabbage  sprouts, 
but  does  not  seem  to  be  a  very  serious  pest,  possibly  because  it  prefers 
the  Cleome.  The  squash  bug,  Anasa  tristis,  is  very  abundant  on  culti- 
vated squashes,  and .  commonly  hibernates  under  yucca  stems  miles 
from  any  cultivated  fields.  The  well-known  Carolina  locust,  Dis- 
sosteira  Carolina,  which  in  the  East  frequents  the  driest  of  situations, 
in  New  Mexico  clings  very  closely  to  the  moist  valleys,  like  other  eastern 
forms  (as  tiger  beetles)  that  occur  also  in  New  Mexico.  In  both  east 
and  west,  however,  the  species  frequents  places  of  about  the  same  degree 
of  humidity.  In  the  Alkaline  Meadow  Society,  the  lesser  migratory 
locust,  Melanoplus  atlanis,  occurs  in  the  more  moist  situations,  and 
damages  alfalfa  in  the  valleys.  The  red-legged  locust  is  common, 
inhabiting  somewhat  drier  situations  than  the  last  species.  Mosquitoes, 
Culex  pipiens,  breed  in  countless  millions  in  the  ponds  that  form  in  the 
valley  whenever  the  Rio  Grande  is  high,  usually  in  May  and  June.  All 
the  mosquitoes  seen  on  the  mesa  come  from  the  valley;  sometimes  they 
are  five  miles  from  any  possible  breeding  place.  They  are  carried  by  a 
gentle  breeze,  but  a  brisk  breeze  causes  them  to  seek  shelter  low  down 
among  the  herbage  and  not  to  venture  forth. 

The  following  species,  of  wide  distribution  and  not  characteristic  of 
any  particular  formation,  are  of  interest  as  occurring  in  New  Mexico, 
because  they  are  some  of  the  most  familiar  insects  of  more  eastern  states 
under  quite  different  climatal  conditions.  Coleoptera. — The  metallic 
leaf-beetle,  Chrysochus  auratus,  occurs  on  Apocynum  as  usual,  but  at  an 
altitude  sometimes  of  ten  to  eleven  thousand  feet.  Euphoria  inda 
occurs  from  the  valley  up  to  the  yellow  pine  association  and  doubtless 
higher.  The  lady-beetle,  Hippodamia  convergens,  is  abundant  every- 
where from  the  tops  of  the  highest  mountains  to  the  lowest  parts  of 
New  Mexico.  Lepidoptera. — Colias  eury theme,  is  common  in  the  moun- 
tains and  in  the  valley  wherever  there  is  damp  soil,  but  is  absent  from 
the  mesa.  The  checkered  white,  Pieris  protodice,  is  found  from  the 
valley  to  the  spruce  association.  The  painted  lady,  Pyrameis  cardui,  is 
abundant  wherever  the  thistle  grows;  and  more  abundant  up  in  the 


404  ENTOMOLOGY 

blue  spruce  association  than  anywhere  else.  Hymenoptera. — The  social 
wasp,  Polistes  variatus,  nests  fronii  the  valley  of  the  Rio  Grande  up  into 
the  spruce  forest  at  eight  thousand  feet.  The  pigeon  Tremex,  T.  columba, 
is  equally  abundant  in  the  cottonwoods  of  the  valley  and  in  the  Douglas 
spruce  of  the  mountains.  Hemiptera. — Gerris  remigis,  the  well  known 
water  strider  of  eastern  states,  is  found  on  all  suitable  ponds  and  streams 
in  both  valley  and  mountains.  The  plant-feeding  bug,  Lygus  pratensis, 
is  as  ubiquitous  here  as  it  is  elsewhere  in  the  United  States. 

VII.  Succession 

"Succession  is  no  doubt  one  of  the  most  important  and  widespread 
of  the  phenomena  discovered  by  the  ecologists  up  to  the  present  time. 
Simply  stated,  it  means  that  on  a  given  fixed  area  organisms  succeed  one 
another,  because  of  changes  in  conditions.  These  changes  make 
impossible  the  continued  existence  of  the  forms  present  at  any  given 
time;  with  the  death  or  migration  of  such  forms,  others  adapted  to  the 
changed  conditions  occupy  the  area,  whenever  such  adapted  forms  are 
available.  The  changes  referred  to  result  from  physical  or  biological 
causes,  or  combinations  of  the  two.  It  is  probable  that  the  causes  of 
the  changes  are  frequently  complex  combinations  of  various  factors. 

"We  have  among  the  physical  causes  changes  in  climate  and  changes 
in  topography.  All  degradation  of  land  is  a  cause  of  succession.  Such 
geological  processes  are  well  understood  and  treated  in  textbooks  on 
geology  and  physiography. 

"The  biological  causes  of  succession  lie  chiefly  in  the  fact  that  organ- 
isms frequently  so  affect  their  environment  that  neither  they  themselves 
nor  their  offspring  can  continue  to  Uve  at  the  point  where  they  are  now 
living.  Every  organism  adds  certain  poisonous  substances  to  its 
surroundings,  and  takes  away  certain  substances  needed  by  itself.  It 
frequently  thus  so  changes  conditions  that  its  offspring  cannot  Hve  and 
grow  to  maturity  in  the  same  locality  as  the  parents.  However,  by 
these  same  processes  it  prepares  the  way  for  other  organisms  which  can 
live  and  grow  in  the  conditions  thus  produced."     (Shelf ord.) 

"The  general  growth  or  evolution  of  environmental  conditions 
and  the  communities  which  belong  to  them  are  included  under  succes- 
sion. The  word  succession  is  used  in  three  distinct  senses.  We  speak 
of  (a)  geological  succession,  (b)  seasonal  succession,  and  (c)  ecological 
succession."     (Shelford.) 

Geological. — "Geological  succession  is  primarily  a  succession  of 
species  throughout  a  period  or  periods  of  geological  time.     It  is  due 


INSECT   ECOLOGY  405 

mainly  to  the  dying-out  of  one  set  of  species  and  the  evolution  of 
others  which  take  their  places,  or  in  some  cases  to  migration." 
(Shelford.) 

Many  species  of  insects  owe  their  present  distribution  primarily  to 
the  phenomena  of  the  glacial  epoch.  An  excellent  example  of  this  is 
the  White  Mountain  butterfly  (page  325).  In  Arkansas  mountains, 
the  "elevation  is  not  sufficient  to  provide  true  boreal  conditions,  but 
does  modify  the  temperature  so  that  certain  species,  abundant  at  the 
north,  and  forced  southward  during  the  glacial  epoch,  have  been  enabled 
to  exist  in  this  latitude  till  the  present  time.  Such  are  the  grasshoppers 
Tettix  hancocki,  Chloealtis  conspersa,  and  Melanoplus  fasciatus." 
(Morse.) 

"The  chief  biological  importance  of  the  Southeastern  United  States, 
comprising  Virginia,  North  and  South  Carolina,  Georgia,  Florida, 
Alabama,  eastern  Tennessee,  and  West  Virginia,  is  connected  with  two 
facts:  First,  this  region  served  during  the  Glacial  Epoch  as  a  refuge  for 
boreal  forms  of  life  which  had  been  pushed  southward  by  the  climatal 
conditions  of  the  Ice  Age,  and  at  the  close  of  that  period  it  became  the 
center  of  dispersal  whence  these  forms  were  able  to  restock  the  opening 
country  at  the  north.  Second,  during  this  later  period  its  lowland 
plains  served,  and  probably  continue  to  serve,  as  a  highway  of  dispersal 
for  austral  forms  entering  the  country  from  the  south  and  southwest, 
many  of  which  have  penetrated  far  into  the  heavily  glaciated  region  of 
the  Northern  States."     (Morse.) 

Seasonal. — "Seasonal  succession  is  the  succession  of  species  or 
stages  in  the  life  histories  of  species  over  a  given  locality,  due  to  heredi- 
tary and  environic  differences  in  the  life  histories  (time  of  appearance) 
of  species  living  there. "  (Shelford.)  "Successful  species  are  those  that 
fit  wJc  the  seasonal  rhythm  with  respect  to  physical  conditions, 
food,  and  numerous  o'-^r  reiatiorxS. "     (Shelford.) 

Many  examples  of  seasonal  succession  among  insects  will  occur 
to  the  student  of  insect  life.  The  seasonal  succession  of  insects  is 
frequently  correlated  with  that  of  plants.  The  cycle  of  an  insect  may 
be  adjusted  to  that  of  a  plant  upon  which  it  depends. 

Thus  "the  Membracidae  or  tree  hoppers  are  celebrated  for  the 
wonderful  variety  and  complexity  of  their  adaptations  to  their  food 
plants.  .  .  .  The  tree  hoppers  of  the  genus  Telamona,  for  example, 
feed  very  largely  on  the  sap  of  the  trees  and  mainly  on  the  tender 
growing  twigs.  They  find  optimum  conditions  for  such  feeding  only 
during  the  comparatively  short  period  in  which  the  tree  is  making  its 


4o6  ENTOMOLOGY 

growth.  They  also  must  find  a  location  and  deposit  their  eggs  while 
the  wood  is  still  soft  and  tender;  otherwise  they  will  be  unable  to 
penetrate  to  a  sufficient  depth  to  protect  the  eggs  from  predaceous  and 
parasitic  insects.  The  result  is  that  we  find  that  they,  with  a  possible 
exception,  pass  the  winter  in  the  egg  .stage  and  have  a  single  annual 
generation.  ...  A  striking  adaptation  to  a  special  period  in  a  plant's 
growth  is  shown  in  the  life  cycle  of  Micrutalis  calva,  the  little  shining 
black  seed-like  tree  hopper.  The  nymphs  are  found  between  the 
branches  of  the  blossom  head  of  the  Ironweed,  Vernonia.  This  purple 
flower  appears  only  in  the  fall,  so  that  the  single  generation  of  nymphs 
comes  on  over  70  days  later  than  its  relative  that  lives  in  the  tree. 

"In  the  case  of  Ceresa  bubalis  (the  Buffalo  tree  hopper)  and  its 
vegetation-feeding  allies  the  need  of  haste  is  not  so  great  as  their  food 
plants,  Composites,  Legumes  and  others,  grow  all  summer,  so  we  find 
the  nymphal  period  both  longer  and  later  and  the  adults  extending  into 
the  fall."     (E.D.Bali.) 

The  time  of  appearance  of  the  locust  borer,  Cyllene  robinice,  in  the 
fall  coincides  with  that  of  the  flowers  of  golden  rod,  on  which  the  beetles 
feed;  the  coloration  of  the  beetles  being  protective,  as  Prof.  H.  Garman 
has  observed  in  Kentucky. 

Ecological.— "  Ecological  succession  of  animals  is  succession  of 
mores  over  a  given  locality  as  conditions  change.  If  species  have  rela- 
tively fixed  mores  we  have  succession  of  species.  When  mores  are 
flexible  we  may  have  the  same  species  remaining  throughout,  with 
changes  in  mores. "     (Shelford.) 

A  few  examples,  from  Shelf ord's  Vegetation  and  the  Control  of  Land 
Animal  Communities,  will  serve  to  illustrate  this  kind  of  succession. 

The  stages  of  forest  development  are  marked  by  the  dominance  of 
certain  species  of  trees  which  succeed  one  another  in  a  rather  definite 
order.  On  the  sand  areas  at  the  head  of  Lake  Michigan,  the  sequence 
is  as  follows  (Cowles).  i.  Cottonwood  Stage.  Near  the  lake  shore, 
with  the  sand  more  or  less  shifting  and  rarely  with  more  than  a  trace  of 
humus.  2.  Pine  Stage.  With  stable  sand,  considerably  blackened  by 
humus,  except  in  blowouts.  2>-  ^^<^(^k  Oak  Stage.  With  the  sand  much 
darkened  by  humus  and  locally  covered  with  a  dry  moss  or  with  dead 
leaves;  grasses  and  a  shrubby  undergrowth  occur.  4.  Red  Oak  Stage. 
Ground  with  a  carpet  of  leaves  and  humus;  with  a  well  marked  shrubby 
and  herbaceous  growth.  Red  oak,  black  oak,  and  white  oak;  often 
hickory  also.  5.  Beech  Stage.  The  mineral  soil  is  covered  with  a 
thick  layer  of  leaves  and  humus.     Fewer  species  of  trees  than  in  the 


INSECT   ECOLOGY 


407 


preceding  stage,  but  a  greater  number  of  species  of  small  shrubs,  with 
a  smaller  number  of  individual  shrubs.  The  trees  close  the  overhead 
spaces  and  make  a  dense  shade,  while  the  lower  forest  is  open.  Beech 
and  sugar  maple  are  characteristic.  These  five  stages  are  linked 
together  by  transitional  stages. 

Of  the  many  species  tabulated  by  Shelford,  the  tiger  beetles  and 
grasshoppers  may  be  selected  to  illustrate  succession  in  relation  to  forest 
development.  The  tiger  beetles,  Cicindela,  breed  in  the  subterranean 
stratum  and  feed  in  the  ground  stratum. 


Tiger  Beetles  of  Forest  Succession  (Shelford) 
In  these  tables  C  signifies  common;  F,  few;  P,  present 


Stage  I 
Cottonwood 


Pine 


Black  Oak 


Red  Oak- 
Hickory 


5 
Beech 


C.  hpida 

C  formosa  generosa. . 
C.  sculellaris  lecontei. 
C.  sex  guttata 


With  the  tiger  beetles  the  character  of  the  soil,  as  regards  suitability 
for  oviposition,  is  the  chief  factor  that  determines  the  presence  or 
absence  of  this  or  that  species.  C.  sexguttata,  which  comes  in  with  the 
white  oak-  red  oak-  hickory  forest,  lays  its  eggs  under  loose  leaves  or  in 
little  irregularities  in  the  ground,  which  contain  a  little  humus  and  are 
slightly  shaded;  it  is  rare,  however,  in  very  shady  situations,  such  as 
those  of  the  beech  and  maple  forest. 

Of  the  orthoptera  named  in  the  following  table,  numbers  i  to  6 
breed  in  the  subterranean  stratum  and  feed  in  the  ground  stratum; 
6  feeds  also  in  the  vegetation  strata;  7  breeds  in  the  ground  stratum, 
feeds  in  the  herbaceous;  8  and  9  breed  and  feed  in  the  herbaceous; 
10  and  II  breed  and  feed  in  the  tree  stratum;  12  breeds  and  feeds  in 
the  subterranean-ground  stratum;  and  13  in  the  ground  stratum. 

The  table  indicates  that  the  successive  changes  in  vegetation  are 
accompanied  by  corresponding  changes  in  the  character  of  the  orthop- 
teran  fauna.  Other  insects  or  other  animals  also  illustrate  the  same 
phenomenon  of  ecological  succession.  During  the  successive  vegeta- 
tional  stages  the  numbers  of  a  species  increase  until  optimum  conditions 
of  habitat  are  attained,  and  thereafter  decrease. 


4o8 


ENTOMOLOGY 
Orthoptera  or  Forest  Succession  (Shelford) 


Stage  I 
Cottonwood 


1-2 

2 

Pine 

2-3 

3 
Black  Oak 

4 
Red  Oak- 
Hickory 

P 

c 

C 

C 

P 

P 

c 

c 

C 

c 

c 

c 

c 

c 

C 

C 

F 
C 

C 

F 
C 

5 
Beech 


1.  Seaside     locust,     Trimerotropis 

marilima 

2.  Long-homed  grasshopper,  Psi- 

nidia  fenesiralis 

3.  Sand    locust,    Agenotettix    are- 

nosus 

4.  Mottled  sand  locust,  Spharage- 

mon  ivyotningarum 

5.  Migratory    locust,    Melanoplus 

atlanis 

6.  Locust,      Melanoplus     angusli- 

pennis 

7-  Sprinkled  locust,  Chloeallis  con- 
sPersa 

8.  Texas    grasshopper,    Scudderia 

texensis 

9.  Tree  cricket,  Oecanthus  fasciatus 
10.  Tree  cricket,  Oecanthus  angusti- 

pennis 

ri.  Katydid,  Cyrtophyllus  perspicil- 

latus 

f2.  Camel  cricket,  Ceuihophilus. .  .  . 
[3.  Locust,  Melanoplus  islandicus.. . 


Some  species  of  insects  do  not  appear  until  the  Black  Oak  stage,  and 
others  not  until  the  Red  Oak-Hickory  or  the  Beech-Maple  stage. 

The  causes  of  animal  succession  and  the  control  of  animal  com- 
munities are  discussed  by  Shelford,  who  draws  these  conclusions,  among 
others. 

"The  development  of  forest  on  sand  or  other  mineral  soil  is  accom- 
panied by  an  almost  complete  change  of  animal  species  and  probably 
by  a  complete  change  of  animal  mores. 

"Forest  development  is  accompanied  by  marked  changes  in  soil 
and  physical  factors;  animal  distribution  is  more  closely  correlated 
with  differences  in  physical  factors  than  with  species  of  plants. 

"Succession  of  all  the  animals  of  the  forest  communities  under 
consideration  is  comparable  in  principle  to  that  in  ppnds.  Succession 
is  due  to  an  increment  of  changes  in  conditions  produced  by  the  plants 
and  animals  living  at  a  given  point.  Animals  through  their  effect 
upon  the  soil  play  an  important  though  minor  part  in  the  process. 

"The  various  animal  species  are  arranged  in  these  communities  in 
an  orderly  fashion  and  the  dominating  animal  mores  are  correlated 
with  the  dominating  conditions. 

"Taxonomic    (structural)    species    usually    have    distinct    mores. 


INSECT    ECOLOGY  409 

though  the  same  species  often  has  different  mores  under  different 
conditions,  and  different  species  may  have  the  same  mores.  Species 
and  mores  are  therefore  not  synonymous. 

"Ecology  considers  together  mores  that  are  alike  or  similar  in 
their  larger  characters." 


CHAPTER  XIV 

INSECTS  IN  RELATION  TO  MAN 

A  great  many  insects,  eminently  successful  from  their  own  stand- 
point, so  to  speak,  nevertheless  interfere  seriously  with  the  interests  of 
man.  On  the  other  hand,  many  insects  are  directly  or  indirectly  so 
useful  to  man  that  their  services  form  no  small  compensation  for  the 
damage  done  by  other  species. 

Injurious  Insects.- — Insects  destroy  cultivated  plants,  infest  do- 
mestic animals,  injure  food,  manufactured  articles,  etc.,  and  molest  or 
harm  man  himself. 

The  cultivation  of  a  plant  in  great  quantity  offers  an  unusual  oppor- 
tunity for  the  increase  of  its  insect  inhabitants.  The  number  of  species 
affecting  one  kind  of  plant — to  say  nothing  of  the  number  of  individuals 
— is  often  great.  Thus  about  200  species  attack  Indian  corn,  50  of 
them  doing  notable  injury;  200  affect  clover,  directly  or  indirectly;  and 
400  the  apple;  while  the  oaks  harbor  probably  1,000  species. 

The  average  annual  loss  through  the  cotton  worm,  i860  to  1874,  was 
$15,000,000,  according  to  Packard;  the  loss  from  the  Rocky  Mountain 
locust,  in  1874,  in  Iowa,  Missouri,  Kansas  and  Nebraska,  $40,000,000 
(Thomas) ;  and  the  total  loss  from  this  pest,  1874  to  1877;  $200,000,000. 
The  loss  through  the  chinch  bug,  in  1864,  was  $73,000,0000  in  Illinois 
alone,  as  estimated  by  Riley.  The  ravages  of  the  Hessian  fly,  fluted 
scale,  San  Jose  scale,  gipsy  moth  and  cotton  boll  weevil  need  only  be 
mentioned. 

At  times,  an  insect  has  been  the  source  of  a  national  calamity,  as  was 
the  case  for  forty  years  in  France,  when  Phylloxera  threatened  to  ex- 
terminate the  vine.  In  Africa  the  migratory  locust  is  an  unmitigated 
evil. 

Probably  at  least  ten  per  cent,  of  every  crop  is  lost  through  the  at- 
tacks of  insects,  though  the  loss  is  often  so  constant  as  to  escape  obser- 
vation. Regarded  as  a  direct  tax  of  ten  cents  upon  the  dollar,  however, 
this  loss  becomes  impressive.  Webster  says:  "It  costs  the  American 
farmer  more  to  feed  his  insect  foes  than  it  does  to  educate  his  children." 
The  average  annual  damage  done  by  insects  to  crops  in  the  United 
States  was  conservatively  estimated  by  Walsh  and  Riley  to  be  $300,000,- 

410 


INSECTS    IN    RELATION    TO    MAN  4II 

000 — or  about  $50  for  each  farm.  "A  recent  estimate  by  experts  put  the 
yearly  loss  from  forest  insect  depredations  at  not  less  than  $100,000,000. 
The  common  schools  of  the  country  cost  in  1902  the  sum  of  $235,000,000, 
and  all  higher  institutions  of  learning  cost  less  than  $50,000,000,  making 
the  total  cost  of  education  in  the  United  States  considerably  less  than 
the  farmers  lost  from  insect  ravages.  Thus  it  would  be  within  the 
statistical  truth  to  make  a  still  more  starthng  statement  than  Webster's, 
and  say  that  it  costs  American  farmers  more  to  feed  their  insect  foes 
than  it  does  to  maintain  the  whole  system  of  education  for  everybody's 
children. 

"Furthermore,  the  yearly  losses  from  insect  ravages  aggregate 
nearly  twice  as  much  as  it  costs  to  maintain  our  army  and  navy;  more 
than  twice  the  loss  by  fire ;  twice  the  capital  invested  in  manufacturing 
agricultural  implements ;  and  nearly  three  times  the  estimated  value  of  the 
products  of  all  the  fruit  orchards,  vineyards,  and  small  fruit  farms  in  the 
country."     (Slingerland.) 

Though  most  of  the  parasites  of  domestic  animals  are  merely  annoy- 
ing, some  inflict  serious  or  even  fatal  injury,  as  has  been  said.  The 
gad  flies  persecute  horses  and  cattle;  the  maggots  of  a  bot  fly  grow  in 
the  frontal  sinuses  of  sheep,  causing  vertigo  and  often  death;  another 
bot  fly  develops  in  the  stomach  of  the  horse,  enfeebling  the  animal. 
The  worst  of  the  bot  flies,  however,  is  Hypoderma  lineata,  the  ox-warble, 
which  not  only  impairs  the  beef  but  damages  the  hide  by  its  perforations ; 
the  loss  from  this  insect  for  one  period  of  six  months  (Chicago,  1889)  was 
conservatively  estimated  as  $3,336,565,  of  which  $667,513  represented 
the  injury  to  hides. 

All  sorts  of  foodstuffs  are  attacked  by  insects,  particularly  cereals; 
clothing,  especially  of  wool,  fur  or  feathers;  also  furniture  and  hundreds 
of  other  useful  articles. 

As  carriers  of  disease  germs,  insects  are  of  vital  importance  toman, 
as  we  have  shown. 

Beneficial  Insects.— The  vast  benefits  derived  from  insects  are  too 
often  overlooked,  for  the  reason  that  they  are  often  so  unobvious  as 
.compared  with  the  injuries  done  by  other  species.  Insects  are  useful 
as  checks  upon  noxious  insects  and  plants,  as  pollenizers  of  flowers,  as 
scavengers,  as  sources  of  human  clothing,  food,  etc.,  and  as  food  for 
birds  and  fishes. 

Almost  every  insect  is  subject  to  the  attacks  of  other  insects,  pre- 
daceous  or  parasitic — to  say  nothing  of  its  many  other  enemies — and 
but  for  this  a  single  species  of  insect  might  soon  overrun  the  earth. 


412  ENTOMOLOGY 

There  are  only  too  many  illustrations  of  the  tremendous  spread  of  an 
insect  in  the  absence  of  its  accustomed  natural  enemies.  One  of  these 
examples  is  that  of  the  gipsy  moth,  artificially  introduced  into  Massa- 
chusetts from  Europe;  another  is  the  fluted  scale,  transported  from 
Australia  to  Cahfornia.  Some  conception  of  the  vast  restricting  influ- 
ence of  one  species  upon  another  may  be  gained  from  the  fact  that  the 
fluted  scale  was  practically  exterminated  in  California  as  the  result  of 
the  importation  from  Australia  of  one  of  its  natural  enemies,  a  lady-bird 
beetle  known  as  Novius  cardinalis.  The  plant  lice,  though  of  un- 
paralleled fecundity,  are  ordinarily  held  in  check  by  a  host  of  enemies 

(P-  379)- 

An  astonishingly  large  number  of  parasites  may  develop  in  the  body 
of  a  single  individual;  thus  over  3,000  specimens  of  a  hymenopterous 
parasite  {Copidosoma  truncatellum)  were  reared  by  Giard  from  a  single 
Plusia  caterpillar. 

Parasites  themselves  are  frequently  parasitized,  this  phenomenon  of 
hyperparasitism  being  of  considerable  economic  importance.  A  bene- 
ficial primary  parasite  may  be  overpowered  by  a  secondary  parasite, 
evidently  to  the  indirect  disadvantage  of  man,  while  the  influence  of  a 
tertiary  parasite  would  be  beneficial  again.  Now  parasites  of  the  third 
order  occur  and  probably  of  the  fourth  order,  as  appears  from  Howard's 
studies,  which  we  have  already  summarized.  Moreover,  parasites  of  all 
degrees  are  attacked  by  predaceous  insects,  birds,  bacteria,  fungi,  etc. 
The  control  of  one  insect  by  another  becomes,  then,  a  subject  of  extreme 
intricacy. 

Insects  render  an  important,  though  commonly  unnoticed,  service 
to  man  in  checking  the  growth  of  weeds.  Indeed,  insects  exercise  a  vast 
influence  upon  vegetation  in  general.  A  conspicuous  alteration  in  the 
vegetation  has  followed  the  invasions  of  the  Rocky  Mountain  locust, 
as  Riley  has  said;  many  plants  before  unnoticed  have  grown  in  profu- 
sion and  many  common  kinds  have  attained  an  unusual  luxuriance. 

As  agents  in  the  cross  pollination  of  flowers,  insects  are  eminently 
important.  Darwin  and  his  followers  have  proved  beyond  question 
that  as  a  rule  cross  pollination  is  indispensable  to  the  continued  vitaHty 
of  flowering  plants;  that  repeated  close  pollination  impairs  their  vigor 
to  the  point  of  extermination.  Without  the  visits  of  bees  and  other 
insects  our  fruit  trees  would  yield  Httle  or  nothing,  and  the  fruit  grower 
owes  these  helpers  a  debt  which  is  too  often  overlooked. 

As  scavengers,  insects  are  of  inestimable  benefit,  consuming  as  they 
do  in  incalculable  quantity  all  kinds  of  dead  and  decaying  animal  and 


INSECTS    TN    RELATION    TO    MAN  413 

vegetable  matter.  This  function  of  insects  is  most  noticeable  in  the 
tropics,  where  the  ants,  in  particular,  eradicate  tons  of  decomposing 
matter  that  man  lazily  neglects. 

Of  insects  that  are  directly  useful  to  man,  the  silkworms  and  the 
several  species  of  honey  bees  are  the  most  important.  Silk  is  most 
valuable  as  a  textile  material,  but  has  minor  uses.  Some  of  the  best 
fishing  lines  are  made  of  silk;  and  the  best  "leaders"- — long,  tapering, 
strong,  and  practically  invisible  in  the  water — are  the  silk  glands  them- 
selves, after  being  stretched  and  dried.  These  leaders  are  imported 
from  the  Mediterranean  region,  but  may  easily  be  made  from  the  glands 
of  our  large  native  silkworms,  such  as  the  Cecropia. 

Though  honey  as  a  food  is  not  as  indispensable  to  us  as  it  was  to  the 
ancients,  immense  quantities  of  it  are  produced  annually,  and  the 
demand  for  it  is  usually  greater  than  the  supply.  Beeswax  has  more 
uses  than  one  might  suppose.  One  of  its  chief  uses  is  for  the  manufac- 
ture of  comb  ''foundation"  for  bee  hives.  Beeswax,  though  rivaled  by 
paraffin  and  ceresin,  is  better  than  these  for  some  purposes.  It  is  used 
in  poHshes  for  furniture,  floors,  carriages,  automobiles,  shoes  and  other 
leather  articles,  and  steel  tools;  as  a  coating  for  shoemaker's  thread  and 
for  steel  nails;  as  an  ingredient  of  some  varnishes;  for  the  insulation  of 
electric  wires,  etc.;  for  church  candles;  salves  and  cosmetics;  in  sealing 
wax  and  grafting  wax;  by  sculptors  for  making  models;  by  dentists  for 
taking  impressions;  and  was  anciently  used  on  writing  tablets. 

Lac,  commonly  used  as  sheUac  and  for  lacquer  and  other  resistant 
varnishes,  is  yielded  by  several  species  of  scale  insects,  but  chiefly 
Tachardia  lacca,  which  is  abundant  in  many  parts  of  India  on  a  variety 
of  plants  (Zizyphus,  Acacia,  Butea,  etc.).  The  lac  is  a  resinous  secre- 
tion, produced  abundantly  by  the  female,  and  forming  with  the  exuviae  a 
protective  covering  over  her  body. 

A  coccid  that  produces  considerable  quantities  of  lac  occurs  in 
Arizona  on  Larrea  mexicana. 

Several  coccids  of  the  genus  Ceroplastes,  in  India  and  China,  produce 
white  wax,  which  is  highly  valued  for  some  purposes  but  has  been 
replaced  by  paraffin  for  other  uses. 

The  brilliant  crimson  pigment  of  the  lac-insect  of  India  is  extracted 
and  known  to  artists  as  "lake." 

The  cochineal  insect,  Dactylopius  coccus,  is  indigenous  to  Mexico, 
but  has  been  transported  with  its  food  plant,  the  prickly  pear,  to  Spain, 
India,  and  elsewhere.  From  the  dried  bodies  of  the  females,  carmine  is 
extracted.     The  cochineal  industry,  which  dates  back  to  the  time  of  the 


414  ENTOMOLOGY 

Aztecs,  attained  an  immense  development  until  some  fifty  years  ago, 
when  it  began  to  decline  with  the  discovery  of  aniline  dyes.  Even  at 
present,  however,  there  is  a  constant  demand  for  cochineal,  which  is  used 
for  coloring  confectionery,  fabrics,  inks,  and  druggists'  preparations. 

The  cottony  cochineal  insect,  Dactylopius  confusus,  ranges  through- 
out the  cactus  region  of  the  United  States,  and  contains  the  same  crim- 
son fluid  as  its  ally. 

The  Greeks  and  Romans  obtained  a  red  dye  from  species  of  Kertnes 
living  on  an  oak.  Galls  of  Cynipidae  were  once  important  as  a  source 
of  ink. 

As  articles  of  human  food,  some  insects  are  highly  nutritious,  but 
are  appreciated  chiefly  by  savages.  Not  exclusively,  however,  for  the 
"manna"  of  bibHcal  times  was  almost  certainly  the  honey-dew  from  a 
coccid.  It  is  still  used  by  Arabs  as  food  under  the  name  of  "man." 
The  flavor  of  the  large  black  carpenter  ants,  Camponotus,  which  can  be 
scooped  up  with  the  hands  in  large  numbers,  appeals  to  some  who  would 
resent  being  called  savages.  White  grubs,  available  in  any  desirable 
quantity,  are  said  to  make  an  excellent  salad,  high  in  protein  content. 
Used  in  connection  with  corn  they  furnish  almost  a  balanced  ration  for 
hogs. 

The  red  Indians  formerly  used  many  kinds  of  insects  as  food. 
Especially  dehcious  was  a  bushel  of  grasshoppers  roasted  in  a  hole  in 
the  ground.  After  all,  the  grasshopper  is  more  attractive  in  appearance 
and  more  refined  in  its  choice  of  food  than  the  much-esteemed  lobster. 
The  Pah  Utes  of  Utah  eke  out  an  existence  on  dried  caterpillars,  and 
annually  flock  from  far  and  near  to  harvest  the  salt-fly  of  the  salt  lakes. 
The  puparia  of  these  flies  {Ephydra  hians)  are  washed  up  on  the  shore  in 
such  enormous  numbers  that  they  can  be  collected  by  hundreds  of 
bushels.  After  the  dirt  is  removed  and  the  puparium  shelled  off,  the 
pupa,  which  is  rather  large,  supplies  a  food  which  is  said  to  be  not  un- 
pleasant to  the  taste  (Aldrich). 

According  to  Dr.  Aldrich,  the  Indians  in  the  vicinity  of  Mono  Lake, 
California,  collect  for  food  the  caterpiUars  of  the  saturniid  moth, 
Coloradia  pandora,  from  a  species  of  pine  tree.  The  great  event  of 
gathering  the  crop  comes,  unfortunately,  only  every  other  year;  as  the 
insect  has  a  two-year  cycle  and  only  one  brood.  The  Indians  dig  a 
trench  around  a  tree,  making  the  outer  wall  of  the  trench  vertical;  then 
beat  the  caterpiUars  off  the  branches  and  collect  them  in  the  trench. 
The  dried  caterpillars  are  a  great  delicacy  to  the  Indians.  Aldrich 
says  they  taste  like  linseed  oil. 


INSECTS    IN    RELATION    TO    MAN  415 

Water-boatmen  {Corixa)  and  their  eggs  are  used  as  food  in  Mexico, 
and  are  said  to  have  a  fine  flavor.  In  Australia  the  Bugong  moth 
occurs  in  millions  in  certain  localities,  and  the  moth  itself  was  formerly 
an  important  article  of  food  with  the  aborigines  (Sharp).  The  bush- 
men  of  Australia  find  that  the  clay  of  termite  mounds  makes  a  solid 
meal;  and  hill  tribes  of  India  eat  the  termites,  which  have  a  flavor  like 
that  of  almonds.  In  Africa  the  migratory  locust  has  been  eaten  since 
history  began. 

The  wise  fisherman  knows  that  certain  kinds  of  insects  are  excellent 
bait  for  fishes,  especially  at  certain  seasons.  The  better  known  of  these 
insects  are  grub  worms,  grasshoppers  and  hellgrammites. 

A  few  insects  have  medicinal  properties.  Coccids  of  the  genus 
Kermes  that  live  on  an  oak  in  the  Mediterranean  region  yield  a  medic- 
inal syrup.  Another  coccid,  Llaveia  axinus,  of  Mexico,  produces  a 
peculiar  substance  known  as  axin.  This  is  used  as  an  external  medic- 
inal application,  and  is  of  considerable  value  as  a  varnish.  (Sharp.) 
Our  native  blister  beetles  and  oil  beetles  possess  a  blistering  or  vesicant 
property,  which  is  due  to  the  presence  of  cantharidin  in  their  blood. 
The  crushed  bodies  of  a  Mediterranean  species  are  still  used  medically 
under  the  name  of  Spanish  fly.  In  China  medicinal  properties  are 
ascribed  to  many  different  kinds  of  insects. 

The  use  of  insects  as  ornaments  must  not  be  forgotten.  Beetles 
with  metallic  colors  or  with  iridescence,  like  the  diamond  beetle  of 
Brazil,  are  made  up  into  jewelry.  A  coccid,  Margarodes  formicarium, 
of  the  West  Indies,  found  in  the  soil,  where  it  lives  on  roots  of  plants  and 
is  often  plowed  up,  resembles  a  pearl,  and  is  strung  into  necklaces,  etc. 
(Comstock.)  The  cucujo  beetles  (Pyrophorus)  of  tropical  America 
are  the  most  brilhantly  luminous  of  insects.  They  are  used  for  orna- 
mental display  and  are  said  to  be  serviceable  as  candles.  Their  diffused 
light  is  pleasing  in  its  quality,  and  it  is  reported  that  "the  smallest 
print  may  be  read  by  moving  one  of  these  insects  along  the  lines." 

The  showy  butterflies,  moths,  and  beetles,  mounted  for  purposes  of 
display,  are  familiar  to  all. 

In  Japan  a  "fire-box"  to  hold  a  charcoal  fire  is  made  from  a  section 
of  a  log,  placed  on  end.  For  this  purpose  a  log  is  frequently  selected 
on  account  of  its  natural  ornamentation  made  by  the  engraver  beetles; 
or  a  screen  may  be  made  of  wood  that  is  carved  with  tunnels  made  by 
termites. 

The  unimportant  use  of  insects  as  playthings  need  only  be  alluded 
to.    In  the  south,  children  amuse  themselves  by  attaching  the  green  June 


41 6  ENTOMOLOGY 

bugs  to    threads  and  letting  them  fly  about.     In  China  crickets  are 
matched  against  each  other  in  fighting  contests. 

Many  other  examples  of  insects  beneficial,  more  or  less,  to  man 
could  be  given  if  space  permitted. 

Doubtless  many  of  us  have  now  and  then  kept  crickets  or  katydids  in 
cages  because  we  liked  to  hear  them  sing;  or  have  put  fire  flies  in  bottles 
to  watch  them  glow. 

The  Japanese,  with  a  national  appreciation  of  nature  which  is 
foreign  to  this  country,  are  accustomed  to  do  these  things.  Crickets 
and  katydids  are  sold  on  the  streets,  at  prices  equivalent  to  two  to 
fifteen  cents  each,  much  as  flowers  are  sold  here. 

As  they  have  a  cherry  blossom  season,  they  have  also  a  fire  fly 
season,  when  it  is  the  common  custom  to  make  visits  to  the  country  to 
procure  fire  flies.     Special  trains  are  even  run  for  these  excursions. 

Annually  the  people  of  Gifu  collect  many  thousands  of  fire  flies, 
which  are  sent  to  Tokyo  and  on  a  certain  night  are  liberated  for  the 
enjoyment  of  the  emperor. 

As  objects  of  scientific  investigation  insects  are  important,  as  no 
entomologist  will  deny.  They  are  even  economically  important  in  this 
respect,  for  some  of  the  principles  of  heredity,  applicable  to  the  breeding 
of  domesticated  animals,  have  been  worked  out  with  the  aid  of  insects, 
particularly  the  pomace  flies,  Drosophila. 

Introduction  and  Spread  of  Injurious  Insects. — Many  of  our  worst 
insect  pests  were  brought  accidentally  from  Europe,  notably  the 
Hessian  fly,  wheat  midge,  codling  moth  (probably),  gipsy  moth, 
brown-tail  moth,  European  corn  borer,  elm  leaf  beetle,  leopard  moth, 
woolly  apple  aphid,  cabbage  butterfly,  cabbage  aphis,  clover  leaf 
beetle,  clover  root  borer,  asparagus  beetle,  imported  currant  worm  and 
many  cutworms;  though  few  American  species  have  obtained  a  foothold 
in  Europe,  one  of  the  few  being  the  dreaded  Phylloxera,  which  appeared 
in  France  in  1863. 

The  gipsy  moth  (Porthetria  dispar) ,  a  native  of  Europe,  where  it  is 
at  times  a  serious  pest,  was  Uberated  in  eastern  Massachusetts  in  1868, 
and  has  spread  over  the  eastern  half  of  the  state  and  into  New  Hamp- 
shire, Maine  and  Connecticut,  in  spite  of  all  efforts  to  control  it.  Small 
infestations  occur  also  in  New  York  and  Pennsylvania,  and  in  July, 
1920,  a  colony  was  found  in  New  Jersey,  where  at  present  (1922)  410 
square  miles  are  infested.  The  cost  of  controlling  this  omnivorous  pest 
is  enormous  (see  beyond).  "The  amount  expended  by  the  Bureau  in 
the  campaign  against  the  Gipsy  Moth,  including  the  appropriation  for 


INSECTS    IN    RELATION    TO    MAN 


417 


the  current  fiscal  year,  is  $4,650,000.  "     (Dr.  L.  O.  Howard,  March  28, 
1922.) 

The  brown-tail  moth  {Euprociis  chrysorrkcea)  is  a  native  of  the  Old 
World  "  where  it  is  found  from  Algiers  on  the  South  to  Sweden  on  the  North 
and  from  England  on  the  West  to  the  Himalaya  Moutains  on  the 
East.  Over  most  of  this  area  it  is  recognized  as  a  pest  of  orchards  and 
forests. "  (Dr.  W.  E.  Britton.)  This  moth  was  accidentally  introduced 
into  eastern  Massachusetts  on  nursery  stock,  and  first  attracted  the 
attention  of  entomologists  in  1897,  since  when  it  has  spread  over  most 
of  Massachusetts  and  New  Hampshire,  into  Vermont,  Maine,  Nova 
Scotia  and  New  Brunswick,  over  all  of  Rhode  Island,  half  of  Connecti- 
cut, and  into  New  York.  The  brown-tail  moth  has  accompanied  the 
gipsy  moth  in  its  work  of  destruction. 

The  brown-tail  moth  spreads  locally  by  means  of  flight,  mostly; 
but  may  be  carried  great  distances  commercially,  on  shipments  of  young 
trees  bearing  young  caterpillars  in  their  winter  nests.  The  first  nests 
found  in  Connecticut  came  on  fruit  tree  seedlings  imported  in  1909 
from  a  French  nursery.  (Britton.)  The  pest  has  several  times  reached 
nurseries  in  Illinois  on  young  trees  from  Belgium  and  France,  but  has 
each  time  been  eradicated  by  the  state  inspection  service  before  it 
could  spread  from  the  nurseries.  In  192 1  the  federal  inspectors  inter- 
cepted nests  of  the  brown-tail  moth  on  forty-two  shipments  from 
France,  and  egg  masses  of  the  gipsy  moth  on  one  shipment. 

These  two  pests  have  been  fought  most  vigorously  but  are  not  yet 
under  complete  control.  It  is  worth  while  to  give  here  an  account  of 
the  expenditures  made  up  to  date  (April  5,  1922)  in  the  fight  against 
the  gipsy  moth  and  the  brown-tail  moth.  Mr.  A.  F.  Burgess,  who  is  in 
charge  of  the  work,  has  kindly  furnished  these  figures. 
Expenditures  by  Infested  States 
(Federal  Funds  Not  Included) 


States 

Expenditures 

From 

beginning 

of  work  to — 

Expenditures 
by  towns,  in- 
dividuals, etc. 

Totals 

Connecticut 

Maine 

Massachusetts 

New  Hampshire 

Rhode  Island 

183,715-55    Dec.  I,  1921 
435,000.00            do 
5,137,000.00            do 

186,500.00    Sept.  30,  1921 
179,600.00    Dec.  31,  1921 
24,409.72           do 
161,883.73           do 
175,000.00            do 

229.50 
180,000.00 
9,126,927.97 
No  record 

20 , 000 . 00 
No  record 

25,000.00 
No  record 
No  record 

183,945.05 
615,000.00 
14,263,927.97 
186,500.00 
199,600.00 

Vermont 

New  Jersey 

24,409.72 
186,883.73 

New  York 

175,000.00 

Pennsylvania 

600 . 00 

do 

600.00 

$6 , 483 , 709 . 00 

$9,352, 157.47  $15,835,866.47 

4l8  ENTOMOLOGY 

Add  to  this  the  amount  supplied  by  the  Federal  Government,  and 
the  total  is  more  than  twenty  million  dollars. 

The  San  Jose  scale  insect  {Aspidiotus  perniciosus) ,  a  native  of  North 
China,  was  introduced  into  the  San  Jose  valley,  California,  about  1870, 
probably  upon  the  flowering  Chinese  peach,  became  seriously  destruc- 
tive there  in  1873,  was  carried  across  the  continent  to  New  Jersey  in 
1886  or  1887  on  plum  stock,  and  thence  distributed  directly  to  several 
other  states  upon  nursery  stock.  At  present  the  San  Jose  scale  is  a 
permanent  menace  to  horticulture  throughout  the  United  States,  and  is 
being  checked  or  subdued  only  by  the  vigorous  and  continuous  work  of 
ojQ&cial  entomologists,  acting  under  special  legislation.  This  pernicious 
insect  occurs  also  in  Japan,  Hawaii,  Australia  and  Chile. 

The  Mexican  cotton  boll  weevil  {Anthonomus  grandis),  which  is 
found  throughout  Mexico  and  in  Guatemala,  Costa  Rica  and  western 
Cuba,  crossed  the  Rio  Grande  river  and  appeared  in  Brownsville, 
Texas,  about  1892.  It  either  flew  across  the  river  or  was  carried  across 
in  seed  cotton.  Since  then  it  has  extended  its  range  every  year  until  in 
1921  it  had  practically  "reached  the  limit  of  cotton  cultivation." 

The  beetle  hibernates  and  lays  its  eggs  in  the  squares  or  bolls  of 
cotton;  these  are  injured  both  by  the  larva  feeding  within  and  by  the 
beetles,  whose  feeding-punctures  destroy  the  bolls  and  cause  them  to 
drop.  The  annual  loss  from  the  weevil  is  far  in  excess  of  $200,000,000. 
The  pest  has  now  been  thoroughly  studied  by  the  Bureau  of  Entomology, 
and  the  adoption  of  the  control  methods  recommended  by  the  Bureau 
enables  cotton  to  be  grown  at  a  fair  profit;  though  the  days  of  "bumper 
crops"  have  gone. 

The  European  corn  borer  {Pyrausta  nubilalis),  long  known  in  Europe 
as  a  pest  of  corn,  hemp,  hops  and  millet,  was  discovered  near  Boston, 
Massachusetts,  in  191 6,  having  been  introduced  probably  in  hemp  sent  to 
a  cordage  factory,  or  in  broom  corn.  In  1919  the  borer  was  found  to 
be  infesting  four  hundred  square  miles  in  the  vicinity  of  Schenectady, 
New  York,  having  arrived  possibly  in  bales  of  broom  corn  from  Austria. 
In  1920  the  insect  had  established  itself  in  an  area  of  nineteen  hundred 
square  miles  in  eastern  Massachusetts,  southern  New  Hampshire,  and 
New  York,  and  appeared  in  Ontario,  Canada.  The  borer  feeds  not  only 
on  cultivated  plants  but  also  on  a  great  variety  of  weeds.  Energetic 
efforts  are  being  made  to  prevent  this  destructive  insect  from  spreading 
westward  into  the  corn  belt. 

The  green  Japanese  beetle  {Popillia  japonica),  which  in  its  native 
home  is  not  an  important  pest,  was  discovered  in  New  Jersey  in  August , 


INSECTS    IN   RELATION   TO   MAN  419 

1 91 6,  and  in  Pennsylvania  in  1920.  It  came  from  Japan  probably  as 
grubs  in  soil  about  the  roots  of  iris  or  azalea  plants,  but  brought  none  of 
its  native  enemies  with  it,  and  spread  rapidly  in  its  new  environment. 
In  192 1  it  occupied  two  hundred  and  thirteen  square  miles  in  New 
Jersey  and  fifty-seven  in  Pennsylvania. 

The  injury  is  done  mostly  by  the  beetles,  which  skeletonize  the  leaves 
of  trees  and  shrubs,  both  wild  and  cultivated,  destroy  ripening  fruits, 
and  have  a  longer  list  of  food  plants  than  the  brown-tail  moth. 

Extensive  operations  against  the  beetle  are  being  conducted  by  the 
Bureau  of  Entomology  in  co-operation  with  the  Departments  of  Agri- 
culture of  New  Jersey  and  Pennsylvania. 

The  elm  leaf  beetle  {Galerucella  luteola),  notorious  in  southern 
Europe  as  a  defoliator  of  elm  trees,  entered  Maryland  about  1837, 
spread  along  the  coast  as  far  as  southern  New  Hampshire,  and  has  made 
its  way  into  New  York,  Ohio  and  Kentucky,  killing  off  thousands  of 
fine  old  elms  on  its  way.  The  only  eft"ective  means  of  controlling  this 
beetle  seems  to  be  an  arsenical  spray. 

The  leopard  moth  {Zeuzera  pyrina) ,  another  European  species  acci- 
dentally introduced  into  New  Jersey  some  time  before  1879,  spread  north 
into  Massachusetts,  assisting  the  elm  leaf  beetle  in  its  injurious  activity. 
The  leopard  moth  is  not  confined  to  elms,  however,  though  it  injures 
chiefly  elms  and  silver  maples,  but  attacks  more  than  eighty  kinds  of 
trees  and  shrubs,  and  affects  fruit  trees  as  well  as  shade  trees.  The  cater- 
pillar does  not  feed  on  the  leaves  but  bores  into  the  branches,  which 
become  weakened  as  a  result  and  are  broken  off  by  the  wind. 

The  pink  bollworm  {Pectinophora  gossypiella) ,  a  cotton  pest  which  is 
probably  a  native  of  southern  Asia  and  occurs  also  in  Africa,  Hawaii 
and  Brazil,  entered  Mexico  and  was  recently  introduced  into  Texas. 
This  serious  pest  is  now  being  eradicated  by  the  Department  of  Agri- 
culture, at  an  annual  expense  of  about  half  a  million  dollars. 

An  insect  often  passes  readily  from  a  wild  plant  to  a  nearly  related 
cultivated  species.  Thus  the  Colorado  potato  beetle  passed  from  the 
wild  species  Solarium  rostratum  to  the  introduced  species,  Solanum 
tuberosum,  the  potato.  Many  of  our  fruit-tree  insects  feed  upon  wild,  as 
well  as  cultivated,  species  of  Rosaceae;  the  peach  borer,  a  native  of  this 
country,  probably  fed  originally  upon  wild  plum  or  wild  cherry.  Many 
of  the  common  scarabaeid  larvae  known  as  'white  grubs  "  are  native  to 
prairie  sod,  and  attack  the  roots  of  various  cultivated  grasses,  including 
corn,  and  those  of  strawberry,  potato  and  other  plants.  The  chinch 
bug  fed  originally  upon  native  grasses,  but  is  equally  at  home  on  cul- 


420  ENTOMOLOGY 

tivated  species,  particularly  millet,  Hungarian  grass,  rice,  wheat, 
barley,  rye  and  corn.  In  fact,  the  worst  corn  insects,  such  as  the  chinch 
bug,  wireworms,  white  grubs  and  cutworms,  are  species  derived  from 
wild  grasses. 

Even  in  the  absence  of  cultivated  plants  their  insect  pests  continue 
to  sustain  themselves  upon  wild  plants,  as  a  rule;  the  larva  of  the 
codling  moth,  for  example,  is  very  common  in  wild  apples  and  wild 
haws. 

The  Economic  Entomologist. — To  mitigate  the  tremendous  dam- 
age done  by  insects,  the  individual  cultivator  is  almost  helpless  without 
expert  advice,  and  the  immense  agricultural  interests  of  this  country 
have  necessitated  the  development  of  the  economic  entomologist,  the 
value  of  whose  services  is  universally  appreciated  by  the  intelligent. 

Almost  every  State  now  has  one  or  more  economic  entomologists, 
responsible  to  the  State  or  else  to  a  State  Experiment  Station,  while  the 
general  Government  attends  to  general  entomological  needs  in  the  most 
comprehensive  and  thorough  manner. 

"It  is  the  special  object  of  the  economic  entomologist,"  says  Dr. 
Forbes,  "to  investigate  the  conditions  under  which  these  enormous 
losses  of  the  food  and  labor  of  the  country  occur,  and  to  determine,  first, 
whether  any  of  them  are  in  any  degree  preventable;  second,  if  so,  how 
they  are  to  be  prevented  with  the  least  possible  cost  of  labor  and  money; 
and,  third,  to  estimate  as  exactly  as  possible  the  expenses  of  such  pre- 
vention, or  to  furnish  the  data  for  such  an  estimate,  in  order  that  each 
may  determine  for  himself  what  is  for  his  interest  in  every  case  arising. 

"The  subject  matter  of  this  science  is  not  insects  alone,  nor  plants 
alone,  nor  farming  alone.  One  may  be  a  most  excellent  entomologist 
or  botanist,  or  he  may  have  the  whole  theory  and  practice  of  agriculture 
at  his  tongue's  end,  and  at  his  fingers'  ends  as  well,  and  yet  be  without 
knowledge  or  resources  when  brought  face  to  face  with  a  new  practical 
problem  in  economic  entomology.  The  subject  is  essentially  that  of 
the  relations  of  these  things  to  each  other;  of  insect  to  plant  and  of  plant 
to  insect,  and  of  both  these  to  the  purposes  and  operations  of  the  farm, 
and  it  involves  some  knowledge  of  all  of  them. 

"As  far  as  the  entomological  part  of  the  subject  is  concerned,  the 
chief  requisites  are  a  familiar  acquaintance  with  the  common  injurious 
insects,  and  especially  a  thorough  knowledge  of  their  life  histories,  to- 
gether with  practical  familiarity  with  methods  of  entomological  study 
and  research.  The  life  histories  of  insects  lie  at  the  foundation  of  the 
whole  subject  of  economic  entomology;  and  constitute,  in  fact,  the 


INSECTS    IN    RELATION    TO    MAN  42 1 

principal  part  of  the  science;  for  until  these  are  clearly  and  completely 
made  out  for  any  given  injurious  species,  we  cannot  possibly  tell  when, 
where  or  how  to  strike  it  at  its  weakest  point. 

"But  besides  this,  we  must  also  know  the  conditions  favorable  and 
unfavorable  to  it;  the  enemies  which  prey  upon  it,  whether  bird  or  insect 
or  plant  parasite;  the  diseases  to  which  it  is  subject,  and  the  effects 
of  the  various  changes  of  weather  and  season.  We  should  make,  in  fact, 
a  thorough  study  of  it  in  relation  to  the  whole  system  of  things  by  which 
it  is  affected.  Without  this  we  shall  often  be  exposed  to  needless  alarm 
and  expense,  perhaps,  in  fighting  by  artificial  remedies,  an  insect  already 
in  process  of  rapid  extinction  by  natural  causes;  perhaps  giving  up  in 
despair  just  at  the  time  when  the  natural  checks  upon  its  career  are  about 
to  lend  their  powerful  aid  to  its  suppression.  We  may  even,  for  lack 
of  this  knowledge,  destroy  our  best  friends  under  the  supposition  that 
they  are  the  authors  of  the  mischief  which  they  are  really  exerting 
themselves  to  prevent.  In  addition  to  this  knowledge  of  the  relations 
of  our  farm  pests  to  what  we  may  call  the  natural  conditions  of  their  life, 
we  must  know  how  our  own  artificial  farming  operations  affect  them, 
which  of  our  methods  of  culture  stimulate  their  increase,  and  which,  if 
any,  may  help  to  keep  it  down.  And  we  must  also  learn  where  strictly 
artificial  measures  can  be  used  to  advantage  to  destroy  them. 

"For  the  life  histories  of  insects,  close,  accurate  and  continuous 
observation  is  of  course  necessary;  and  each  species  studied  must  be  fol- 
lowed not  only  through  its  periods  of  destructive  abundance,  when  it 
attracts  general  attention,  but  through  its  times  of  scarcity  as  well,  and 
season  after  season,  and  year  after  year. 

"The  observations  thus  made  must  of  course  be  collected,  collated 
and  most  cautiously  generahzed,  with  constant  reference  to  the  con- 
ditions under  which  they  were  made.  No  part  of  the  work  requires 
more  care  than  this. 

"This  work  becomes  still  more  difficult  and  intricate  when  we  pass 
from  the  simple  life  histories  of  insects  to  a  study  of  the  natural  checks 
upon  their  increase.  Here  hundreds  and  even  thousands  of  dissections 
of  insectivorous  birds  and  predaceous  insects  are  necessary,  and  a  care- 
ful microscopic  study  of  their  food,  followed  by  summaries  and  tables 
of  the  principal  results,  a  tedious  and  laborious  undertaking,  a  specialty 
in  itself,  requiring  its  special  methods  and  its  special  knowledge  of  the 
structures  of  insects  and  plants,  since  these  must  be  recognized  in  frag- 
ments, while  the  ordinary  student  sees  them  only  entire. 

"If  we  would  understand  the  relations  of  season  and  weather  to  the 


42  2  ENTOMOLOGY 

abundance  of  injurious  insects,  we  are  led  up  to  the  science  of  meteor- 
ology; and  if  we  undertake  to  master  the  obscure  subject  of  their  diseases, 
especially  those  of  epidemic  or  contagious  character,  we  shall  find  use 
for  the  highest  skill  of  the  microscopist,  and  the  best  instruments  of 
microscopic  research. 

"All  these  investigations  are  preliminary  to  the  practical  part  of  our 
subject.  What  shall  the  farmer  do  to  protect  his  crops?  To  answer 
this  question,  besides  the  studies  just  mentioned,  much  careful  experi- 
ment is  necessary.  All  practical  methods  of  fighting  the  injurious  insects 
must  be  tried — first  on  a  small  scale,  and  under  conditions  which  the 
experimenter  can  control  completely,  and  then  on  the  larger  scale  of 
actual  practice;  and  these  experiments  must  be  repeated  under  varying 
circumstances,  until  we  are  sure  that  all  chances  of  mistake  or  of  acci- 
dental coincidence  are  removed.  The  whole  subject  of  artificial  remedies 
for  insect  depredations,  whether  topical  applications  or  special  modes  of 
culture,  must  be  gone  over  critically  in  this  way.  So  many  of  the  so- 
called  experiments  upon  which  current  statements  relating  to  the  value 
of  remedies  and  preventives  are  based  have  been  made  by  persons 
unused  to  investigation,  ignorant  of  the  habits  and  the  transformations 
of  the  insects  treated,  without  skill  or  training  in  the  estimation  of  evi- 
dence, and  failing  to  understand  the  importance  of  verification,  that  the 
whole  subject  is  honeycombed  with  blunders.  Popular  remedies  for 
insect  injuries  have,  in  fact,  scarcely  more  value,  as  a  rule,  than  popular 
remedies  for  disease. 

"Observation,  record,  generalization,  experiment,  verification — 
these  are  the  processes  necessary  for  the  mastery  of  the  subject,  and 
they  are  the  principal  and  ordinary  processes  of  all  scientific  research." 

The  official  economic  entomologist  uses  every  means  to  reach  the 
public  for  whose  benefit  he  works.  Bulletins,  circulars  and  reports, 
embodying  most  serviceable  information,  are  distributed  freely  where 
they  will  do  the  most  good,  and  timely  advice  is  disseminated  through 
newspapers  and  agricultural  journals.  An  immense  amount  of  corre- 
spondence is  carried  on  with  individual  seekers  for  help,  and  personal 
influence  is  exerted  in  visits  to  infested  localities  and  by  addresses  before 
agricultural  meetings.  Special  emergencies  often  tax  every  resource 
of  the  official  entomologist,  especially  if  he  is  hampered  by  inadequate 
legislative  provision  for  his  work.  Too  often  the  public,  disregarding 
the  prophetic  voice  of  the  expert,  refuses  to  "close  the  door  until  the 
horse  is  stolen." 

Aside  from  these  emergencies,  such  as  outbreaks  of  the  Rocky  Moun- 


INSECTS    IN    RELATION   TO   MAN  423 

tain  locust,  chinch  bug,  Hessian  fly,  San  Jose  scale  and  others,  the  State 
or  Experiment  Station  entomologist  has  his  hands  full  in  any  State  of 
agricultural  importance;  in  fact,  can  scarcely  discharge  his  duties  prop- 
erly without  the  aid  of  a  corps  of  competent  assistants. 

This  chapter  would  be  incomplete  without  some  mention  of  the 
progress  of  economic  entomology  in  this  country,  especially  since 
America  is  pre-eminently  the  home  of  the  science.  The  history  of  the 
science  is  largely  the  history  of  the  State  and  Government  entomologists, 
for  the  following  account  of  whose  work  we  are  indebted  chiefly  to  the 
writings  of  Dr.  Howard,  to  which  the  reader  is  referred  for  additional 
details  as  well  as  for  a  comprehensive  review  of  the  status  of  economic 
entomology  in  foreign  countries. 

Massachusetts. — Dr.  Thaddeus  W.  Harris,  though  preceded  as  a 
writer  upon  economic  entomology  by  William  D.  Peck,  was  our  pioneer 
official  entomologist — official  simply  in  the  sense  that  his  classic  volume 
was  prepared  and  published  at  the  expense  of  the  state  of  Massachu- 
setts, first  (1841)  as  a  "Report"  and  later  as  a  "Treatise."  The 
splendid  Flint  edition  (1862),  entitled  "A  Treatise  on  Some  of  the 
Insects  Injurious  to  Vegetation,"  is  still  "the  vade  mecum  of  the  working 
entomologist  who  resides  in  the  northeastern  section  of  the  country." 

Dr.  Alpheus  S.  Packard  gave  the  state  three  short  but  useful  reports 
from  1871  to  1873. 

As  entomologist  to  the  Hatch  Experiment  Station  of  the  Massachu- 
setts Agricultural  College,  Prof.  Charles  H.  Fernald  issued  important 
bulletins  upon  injurious  insects,  and  published  in  collaboration 
with    Edward  H.  Forbush  a  notable  volume  upon  the  gipsy  moth. 

New  York. — Dr.  Asa  Fitch,  appointed  in  1854  by  the  New  York  State 
Agricultural  Society,  under  the  authorization  of  the  legislature,  was  the 
first  entomologist  to  be  officially  commissioned  by  any  state.  His 
fourteen  reports  (1855  to  1872)  embody  the  results  of  a  large  amount  of 
painstaking  investigation. 

In  188 1  Dr.  James  A.  Lintner  became  state  entomologist  of  New 
York.  Highly  competent  for  his  chosen  work,  Lintner  made  every 
eft'ort  to  further  the  cause  of  economic  entomology,  and  his  thirteen 
reports,  accurate,  thorough  and  extremely  serviceable,  rank  among  the 
best.  Lintner  has  had  a  most  able  successor  in  Dr.  E.  P.  Felt,  who  is 
continuing  the  work  with  exceptional  vigor  and  the  most  careful  regard 
for  the  entomological  welfare  of  the  state.  Felt  has  published  at  this 
writing  thirty-eight  bulletins  (including  twenty-one  annual  reports), 
besides  important  papers  on  forest  and  shade-tree  insects,  and  has 


424  ENTOMOLOGY 

directed  the  preparation  by  Needham  and  his  associates  of  three  notable 
volumes  on  aquatic  insects. 

The  Cornell  University  Agricultural  Experiment  Station,  established 
in  1879,  has  issued  many  valuable  publications  upon  injurious  insects, 
written  by  the  master-hand  of  Professor  Comstock  or  else  under  his 
influence.  The  studies  of  Comstock  and  Slingerland  were  always  made 
in  the  most  conscientious  spirit  and  their  bulletins — original,  thorough 
and  practical — are  models  of  what  such  works  should  be. 

More  recently,  Prof.  C.  R.  Crosby  and  Prof.  G.  W.  Herrick,  of  Cor- 
nell, have  published  important  contributions  to  economic  entomology. 

The  Geneva  station  has  issued  many  excellent  entomological 
bulletins,  the  results  of  investigations  by  V.  H.  Lowe,  F.  A.  Sirrine, 
H.  E.  Hodgkiss,  P.  J.  Parrott,  and  W.  J.  Schoene. 

Illinois. — Mr.  Benjamin  D.  Walsh,  engaged  in  1867  by  the  lUinois 
State  Horticultural  Society,  published  in  1868,  as  acting  state  entomolo- 
gist, a  report  in  the  interests  of  horticulture — an  accurate  and 
altogether  excellent  piece  of  original  work.  Like  many  other  economic 
entomologists  he  was  a  prolific  writer  for  the  agricultural  press  and  his 
contributions,  numbering  about  four  hundred,  were  in  the  highest  degree 
scientific  and  practical. 

Walsh  was  succeeded  by  Dr.  William  LeBaron,  who  published  (187 1 
to  1874)  four  able  reports  of  great  practical  value.  In  the  words  of  Dr. 
Howard,  "He  records  in  his  first  report  the  first  successful  experiment 
in  the  transportation  of  parasites  of  an  injurious  species  from  one  locality 
to  another,  and  in  his  second  report  recommended  the  use  of  Paris  green 
against  the  canker  worm  on  apple  trees,  the  legitimate  outcome  from 
which  has  been  the  extensive  use  of  the  same  substance  against  the 
codling  moth,  which  may  safely  be  called  one  of  the  great  discoveries 
in  economic  entomology  of  late  years." 

Following  LeBaron  as  state  entomologist.  Rev.  Cyrus  Thomas  and 
his  assistants,  G.  H.  French  and  D.  W.  Coquillett,  produced  a  creditable 
series  of  six  reports  (1875  to  1880)  as  part  of  a  projected  manual  of  the 
economic  entomology  of  Illinois. 

In  1882  Prof.  S.  A.  Forbes  was  appointed  state  entomologist.  His 
reports  and  bulletins,  based  upon  the  labors  of  an  able  corps  of  assist- 
ants, are  among  the  best  that  have  been  produced.  Of  the  eighteen 
reports  issued  by  Dr.  Forbes,  those  dealing  with  the  chinch  bug,  San 
Jose  scale,  corn  insects  and  sugar  beet  insects  are  especially  noteworthy. 

The  oflEice  of  state  entomologist  was  discontinued  in  191 7,  without, 
however,  any  interruption  of  the  entomological  work,  which  is  now 


INSECTS    IN    RELATION    TO    MAX  425 

carried  on  by  Dr.  Forbes,  as  director  of  the  Natural  History  Survey, 
with  W.  P.-  Flint  as  chief  entomologist. 

Missouri. — Appointed  in  1868,  Prof.  Charles  V.  Riley  published 
(1869  to  1877)  nine  reports  as  state  entomologist.  To  quote  Dr.  How- 
ard. "They  are  monuments  to  the  state  of  Missouri,  and  more  especially 
to  the  man  who  wrote  them.  They  are  original,  practical  and  scientific. 
.  .  .  They  may  be  said  to  have  formed  the  basis  for  the  new  economic 
entomology  of  the  world."  Riley's  subsequent  work  will  presently  be 
spoken  of. 

Minnesota. — The  reports  that  Dr.  O.  Lugger  issued  in  Minnesota, 
though  compiled  for  the  most  part,  contain  much  serviceable  informa- 
tion, presented  in  a  popularly  attractive  manner.  Following  Lugger, 
F.  L.  Washburn  published  several  useful  reports.  The  present  state 
entomologist  is  Prof.  A.  G.  Ruggles. 

New  Jersey. — New  Jersey  has  long  been  active  and  progressive  in 
state  entomological  work.  Dr.  J.  B.  Smith,  state  entomologist  from 
1894  until  his  death  in  1912.  was  a  most  energetic  investigator  and 
prolific  writer  of  useful  bulletins  and  reports.  He  was  succeeded  by  Dr. 
T.  J.  Headlee,  well  known  for  his  work  in  Kansas. 

Connecticut. — Dr.  W.  E.  Britton  has  published  twenty  reports  as 
state  entomologist.  These  are  of  a  high  degree  of  excellence,  are  well 
illustrated,  and  are  most  useful  treatises  on  the  injurious  insects  of 
the  state. 

Maine. — Dr.  C.  H.  Fernald  and  Prof.  F.  L.  Harvey  formerly 
rendered  entomological  service  to  the  state  of  Maine.  The  work  is  now 
in  the  efficient  hands  of  Dr.  Edith  M.  Patch,  an  authority  on  Aphididae, 
who  has  made  a  reputation  for  the  state  by  her  excellent  publications 
and  those  of  her  co-workers. 

California. — The  progressive  spirit  of  California  has  been  carried 
into  the  entomological  work  of  the  state.  Many  excellent  investiga- 
tions, chiefly  upon  insects  affecting  citrus  plants  and  the  grape,  and 
upon  means  of  control,  have  been  made  by  Prof.  C.  W.  Woodworth, 
Prof.  W.  B.  Herms,  Prof.  H.  J.  Quayle,  and  Prof.  E.  O.  Essig. 

Ohio. — F.  M.  Webster  became  known  as  one  of  the  leading  investiga- 
tors in  economic  entomology  by  his  work  in  Ohio.  Since  then  Prof. 
H.  A.  Gossard  and  J.  S.  Houser  have  made  important  contributions  to 
the  literature  of  economic  entomology. 

Kansas. — Manhattan,  Kansas,  is  a  well-known  center  of  entomolog- 
ical activity,  from  which  have  appeared  many  important  publications  on 
economic  entomology.     Prof.   G.  A.  Dean,  Dr.  J.  H.  Merrill,  and  Dr. 


426  ENTOMOLOGY 

R.  C.  Smith,  with  their  efficient  assistants,  are  carrying  on  the  work 
there.  At  the  University  of  Kansas,  Prof.  S.  J.  Hunter  is  in  charge  of 
entomological  work. 

Iowa. — At  Ames,  Iowa,  Prof.  H.  E.  Summers  was  formerly  state 
entomologist,  followed  by  R.  L.  Webster  as  acting  state  entomologist, 
who  was  succeeded  by  Dr.  E.  D.  Ball,  now  Director  of  Research  of 
the  U.  S.  Department  of  Agriculture.  All  these  men,  with  Dr.  C.  P. 
Gillette  (now  of  Colorado)  and  Prof.  Herbert  Osborn  (now  of  Ohio), 
have  greatly  aided  entomological  progress  by  their  studies. 

Other  States. — The  states  just  mentioned  are  those  in  which 
economic  entomology  has  long  been  encouraged  and  developed.  In 
almost  all  the  other  states,  however,  the  value  of  the  science  is  at  present 
appreciated.  In  the  following  states  the  work  of  the  entomologists  who 
are  named  has  been  especially  noteworthy.  Alabama:  Dr.  W.  E.  Hinds. 
Delaware:  Prof.  E.  D.  Sanderson.  Prof.  C.  0.  Houghton.  Florida: 
Prof.  P.  H.  Rolfs.  Prof.  H.  A.  Gossard.  Idaho:  Prof.  J.  M.  Aldrich. 
Indiana:  Prof.  W.  S.  Blatchley.  Prof.  J.  J.  Davis.  Kentucky:  Prof. 
H.  Garman.  Louisiana:  Prof.  H.  A.  Morgan.  Wilmon  Newell. 
Maryland:  W.  G.  Johnson.  Prof.  T.  B.  Symons.  Massachusetts: 
Prof.  C.  H.  Fernald.  Prof.  H.  T.  Fernald.  Michigan:  Prof.  A.  J.  Cook. 
Prof.  R.  H.  Pettitt.  Mississippi:  Prof.  G.  W.  Herrick.  Prof.  R.  W. 
Harned.  Missouri:  Prof.  J.  M.  Stedman.  Montana:  Prof.  R.  A. 
Cooley.  Nebraska:  Prof.  L.  Bruner.  Prof.  M.  H.  Swenk.  Nevada: 
Prof.  S.  B.  Doten.  New  Hampshire:  Dr.  C.  M.  Weed.  Prof.  E.  D. 
Sanderson.  Prof.  W.  C.  O'Kane.  New  Mexico:  Prof.  C.  H.  T. 
Townsend.  Prof.  T.  D.  A.  Cockerell.  North  Carolina:  Prof.  F. 
Sherman,  Jr.  Oregon:  Dr.  A.  B.  Cordley.  South  Carolina:  Prof.  A.  F. 
Conradi.  Tennessee:  Dr.  H.  A.  Morgan.  Washington:  Prof.  A.  L. 
Melander.     West  Virginia:  Dr.  A.  D.  Hopkins.     Prof.  L.  M.  Peairs. 

State  Experiment  Stations.^The  organization  of  State  Agri- 
cultural Experiment  Stations  in  1888,  under  the  Hatch  Act,  gave 
economic  entomology  an  additional  impetus.  At  present  at  least  one 
experiment  station  is  in  operation  in  every  state  and  territory;  there 
being  stations  in  Alaska,  Hawaii,  Porto  Rico,  Virgin  Islands,  and 
Guam.  These  stations,  often  in  connection  with  state  agricultural 
colleges,  maintain  altogether  more  than  two  hundred  workers  in  en- 
tomology, and  have  issued  a  great  number  of  bulletins  upon  injurious 
insects.  These  publications  are  extremely  valuable  as  a  means  of  dis- 
seminating entomological  information,  and  most  of  them  are  based 
upon   the  investigations  of  their  authors. 


INSECTS    IN    RELATION   TO   MAN  427 

While  these  workers  have  been  conspicuously  active  in  the  publica- 
tion of  their  investigations,  there  are  many  other  station  entomologists 
and  state  entomologists  who  devote  themselves  entirely  to  the  practical 
application  of  entomological  knowledge,  and  whose  work  in  this  respect 
is  highly  important,  even  though  its  influence  does  not  extend  beyond 
the  limits  of  the  state. 

The  U.  S.  Entomological  Commission. — This  commission,  founded 
under  a  special  Act  of  Congress  in  1877  ^o  investigate  the  Rocky  Moun- 
tain locust,  consisted  of  Dr.  C.  V.  Riley,  Dr.  A.  S.  Packard  and  Rev. 
Cyrus  Thomas,  remained  in  existence  until  188 1,  and  pubHshed'five 
reports  and  seven  bulletins,  all  of  lasting  value.  The  first  two  reports 
form  a  most  elaborate  monograph  of  the  Rocky  Mountain  locust;  the 
third  report  includes  important  work  upon  the  army  worm  and  the 
canker  worm;  the  fourth,  written  by  Riley,  is  an  admirable  volume  on 
the  cotton  worm  and  boll  worm;  and  the  fifth,  by  Packard,  is  a  useful 
treatise  on  forest  and  shade-tree  insects. 

The  U.  S.  Department  of  Agriculture.- — The  first  entomological 
expert  appointed  under  the  general  government  was  Townend  Glover, 
in  1854.  He  issued  a  large  number  of  reports  (1863-1877),  which  ''are 
storehouses  of  interesting  and  important  facts  which  are  too  little  used 
by  the  working  entomologists  of  to-day,"  as  Howard  says.  Glover 
prepared,  moreover,  a  most  elaborate  series  of  illustrations  of  North 
American  insects,  at  an  enormous  expense  of  labor,  out  of  all  proportion, 
however,  to  the  practical  value  of  his  undertaking. 

Glover  was  succeeded  in  1878  by  Riley,  whose  achievements  have 
aroused  international  admiration.  He  resigned  in  a  year,  after  writing 
a  report,  and  was  succeeded  by  Prof.  Comstock,  who  held  office  for  two 
years,  during  which  he  wrote  two  important  volumes  (published  re- 
spectively in  1880  and  1881)  dealing  especially  with  cotton,  orange  and 
scale  insects.  His  work  on  scale  insects  laid  the  foundation  for  all  our 
subsequent  investigation  of  the  subject. 

Riley,  assuming  the  office  of  government  entomologist,  published  up 
to  1894,  "12  annual  reports,  31  bulletins,  2  special  reports,  6  volumes  of 
the  periodical  bulletin  Insect  Life  and  a  large  number  of  circulars  of 
information."  During  his  vigorous  and  enterprising  administration 
economic  entomology  took  an  immense  step  in  advance.  The  life 
histories  of  injurious  insects  were  studied  with  extreme  care  and  many 
valuable  improvements  in  insecticides  and  insecticide  machinery  were 
made.  One  of  the  notable  successes  of  Dr.  Riley  and  his  co-workers, 
which  has  attracted  an  exceptional  amount  of  public  attention,  was  the 


428  ENTOMOLOGY 

practical  extermination  of  the  fluted  scale  {Icerya  purchasi),  which 
threatened  to  put  an  end  to  the  cultivation  of  citrus  trees  in  California. 
This  disaster  was  averted  by  the  importation  from  Australia,  in  1888,  of 
a  native  enemy  of  the  scale,  namely  the  lady-bird  beetle  Novius  ( Vedalia) 
cardinalis,  which,  in  less  than  eighteen  months  after  its  introduction 
into  California,  subjugated  the  noxious  scale  insect.  The  United  States 
has  since  sent  Novius  to  South  Africa,  Egypt  and  Portugal  with  similar 
beneficial  results. 

The  Department  of  Agriculture  succeeded  in  starting  a  new  and  im- 
portant industry  in  California — the  culture  of  the  Smyrna  fig.  The 
superior  flavor  of  this  variety  is  due  to  the  presence  of  ripe  seeds,  in  other 
words,  to  fertilization,  and  for  this  it  is  necessary  for  pollen  of  the  wild 
fig,  or  ''caprifig,"  to  be  transferred  to  the  flowers  of  the  Smyrna  fig. 
Normally  this  pollination,  or  *'  caprification,"  is  dependent  upon  the  serv- 
ices of  a  minute  chalcid,  Blastophaga  grossorum,  which  develops  in  the 
gall-like  flowers  of  the  caprifig.  The  female  insect,  which  in  this  excep- 
tional instance  is  winged  while  the  male  is  not,  emerges  from  the  gall 
covered  with  pollen,  enters  the  young  flowers  of  the  Smyrna  fig  to  ovi- 
posit, and  incidentally  pollenizes  them. 

After  many  discouraging  attempts,  Blastophaga,  imported  from 
Algeria,  was  established  in  California,  and  the  new  industry  has  devel- 
oped rapidly. 

Based  upon  the  foundation  laid  by  Riley,  the  work  of  the  Bureau 
of  Entomology  has  steadily  progressed,  under  the  leadership  of  Dr. 
Leland  0.  Howard.  With  a  comprehensive  and  firm  grasp  of  his  sub- 
ject, alert  to  discover  and  develop  new  possibilities,  energetic  and 
resourceful  in  management.  Dr.  Howard  has  brought  the  government 
work  in  applied  entomology  to  its  present  position  of  commanding 
importance.  Admirably  organized,  the  Bureau  now  (1922)  requires 
the  services  of  460  employes,  386  of  whom  are  directly  engaged  in 
scientific  work. 

In  the  magnitude  and  importance  of  its  contributions  to  economic 
entomology  the  Bureau  is  unapproached  by  any  other  organization. 

The  Bureau  of  Entomology  has  always  secured  the  services  of  the 
best  entomologists  avaflable,  and  its  staff  of  experts  includes  many  of 
the  leading  entomologists  of  the  world.  Those  in  charge  of  the  work 
are  as  follows:  Dr.  L.  O.  Howard,  entomologist  and  chief  of  bureau. 
C.  L.  Marlatt,  entomologist  and  assistant  chief  of  bureau.  W.  D. 
Hunter,  southern  field  crop  insect  investigations.  W.  R.  Walton, 
cereal  and  forage  insect  investigations.     Prof.  A.  L.  Quaintance,  decidu- 


INSECTS    IN    RELATION    TO    MAN  429 

ous-fruit  insect  investigations,  tropical  and  subtropical  fruit  insect 
investigations.  C.  L.  Marlatt,  investigations  of  the  Mediterranean 
and  other  fruit  flies.  Dr.  F.  H.  Chittenden,  truck-crop  insect  investiga- 
tions. E.  A..  Back,  stored-product  insect  investigations.  Dr.  A.  D. 
Hopkins,  forest  insect  investigations.  Dr.  L.  O.  Howard,  W.  D.  Hun- 
ter, and  J.  L.  Webb,  investigations  of  insects  affecting  the  health  of 
man  and  animals.  Dr.  E.  F.  Phillips,  investigations  in  bee  culture. 
A.  F.  Burgess,  gipsy  moth  and  brown-tail  moth  investigations. 

The  U.  S.  Department  of  Agriculture  publishes  annually  a  List  of 
Workers  in  Subjects  Pertaining  to  Agriculture,  which  contains  the  names 
of  all  the  entomological  workers  in  the  Department  of  Agriculture,  in 
State  Agricultural  Colleges  and  in  Experiment  Stations. 

Canada. — The  development  of  economic  entomology  in  Canada 
was  due  largely  to  the  efforts  of  Dr.  James  Fletcher,  of  the  Dominion 
Experimental  Farms,  Ottawa,  whose  annual  reports  and  other  writings 
were  of  exceptional  value.  His  work  was  furthered  in  every  way  by 
the  "eminent  director  of  the  experimental  farms  system.  Dr.  William 
Saunders,  himself  a  pioneer  in  economic  entomology  in  Canada  and  the 
author  of  one  of  the  most  valuable  treatises  upon  the  subject  that  has 
ever  been  published  in  America."  Dr.  Fletcher  was  Government  ento- 
mologist from  1884  until  his  death,  in  1908.  Dr.  C.  Gordon  Hewitt, 
who  was  appointed  Dominion  entomologist  in  1909,  made  in  ten  years  a 
brilliant  record  in  public  service.  His  remarkable  work  was  cut  short 
by  his  death  in  February,  1920.  In  October,  1920,  Arthur  Gibson  was 
made  Dominion  entomologist.  He  is  well  fitted  by  ability  and  experience 
to  maintain  the  standard  of  excellence  set  by  his  eminent  predecessors. 

Outside  of  the  government  work,  entomology  in  Canada  centers 
around  the  Entomological  Society  of  Ontario,  whose  excellent  publica- 
tions, sustained  by  the  government,  are  of  great  scientific  and  educa- 
tional importance.  In  addition  to  its  annual  reports,  this  society 
issues  the  Canadian  Entomologist,  one  of  the  leading  serials  of  its 
kind,  edited  for  many  years  by  its  founder,  the  Rev.  C.  J.  S.  Bethune, 
whose  devoted  services  have  been  appreciated  by  every  entomologist. 

The  Association  of  Official  Economic  Entomologists.— Organ- 
ized in  1889  by  a  few  energetic  workers,  this  association  has  had  a  rapid 
and  healthy  growth  and  now  numbers  among  its  members  all  the  leading 
economic  entomologists  of  America  and  a  large  number  of  foreign  work- 
ers. The  annual  meetings  of  the  association  impart  a  vigorous  stimulus 
to  the  individual  worker  and  tend  to  promote  a  well-balanced  develop- 
ment of  the  science  of  economic  entomology. 


LITERATURE 

The  literature  on  entomological  subjects  now  numbers  about  150,000  titles.  The 
works  listed  below  have  been  selected  chiefly  on  account  of  their  general  usefulness  and 
accessibility.  Works  incidentally  containing  important  bibliographies  of  their  special 
subjects  are  designated  each  by  an  asterisk — *. 

BIBLIOGRAPHICAL  WORKS 

Hagen,  H.  A.  Bibliotheca  Entomologica.  2  vols.  Leipzig,  186 2- 1863.  Covers  the  entire 
literature  of  entomology  up  to  1862, 

Englemann,  W.  Bibliotheca  Historico-Naturalis.  i  vol.  Leipzig,  1846.  Literature 
1 700-1846. 

Carus,  J.  v.,  and  Englemann,  W.  Bibliotheca  Zoologica.  2  vols.  Leipzig,  186 1.  Litera- 
ture, I 846-1 860. 

Taschenberg,  O.  Bibliotheca  Zoologica.  5  vols.  Leipzig,  1887-1899.  Vols.  2  and  3, 
entomological  literature,  1861-1880. 

The  Zoological  Record.    London.     Annually  since  vol.  for  1864. 

Catalogue  of  Scientific  Papers,  Royal  Society.    London.     Since  1868. 

Zoologischer  Anzeiger.  Leipzig.  Fortnightly  since  1878.  Bibliographica  Zoologica, 
annual  volumes  since  1896. 

Concilium  Bibliographictmi.  Zurich.  Card  catalogue  of  current  zoological  literature 
since  1896. 

Archiv  fiir  Naturgeschichte.     Berlin.     Annual  summaries  since  1835. 

Journal  of  the  Royal  Microscopical  Society.  London.  Summaries  of  the  most  important 
works,  beginning  1878. 

Zoologischer  Jahresbericht.    Leipzig.     Yearly  summaries  of  literature  since  1879. 

Zoologisches  Centralblatt.    Leipzig.     Reviews  of  more  important  literature  since  1895. 

Psyche.  Cambridge,  Mass.  Records  of  American  literature.  Also  earlier  records, 
beginning  1874. 

Entomological  News. — Philadelphia,  1890  to  date.     Records  of  current  literature. 

BibUography  of  the  more  important  contributions  to  American  Economic  Entomology. 
8  parts.  Pts.  1-5  by  S.  Henshaw;  pts.  6-8  by  N.  Banks.  1318  pp.  Washington, 
1889-1905. 

Banks,  N.  1917.  Index  to  the  Literature  of  American  Economic  Entomology.  Jan.  i, 
1905  to  Dec.  31,  1914.  5  +  323  pp.  Amer.  Assoc.  Econ.  Ent.  Melrose  Highlands, 
Mass. 

Colcord,  M.  1921.  Index  II  to  the  Literature  of  American  Economic  Entomology.  Jan. 
1, 1915  to  Dec.  21,  1919.  4  +  388  pp.  Amer.  Assoc.  Econ.  Ent.  Melrose  High- 
lands, Mass. 

Review  of  Applied  Entomology.  1913  to  date.  Series  A:  Agricultural.  Series  B :  Medical 
and  Veterinary.  Imperial  Bureau  of  Entomology.  London.  Dulau  &  Co.,  Ltd. 
Reviews  of  current  literature. 

Catalogue  of  Scientific  Serials,  1633-1876.  S.  H.  Scudder.  Cambridge,  Mass.  Harvard 
University,  1879. 

A  Catalogue  of  Scientific  and  Technical  Periodicals,  1665-1895.     H.  C.  Bolton.     Wash- 
ington, Smithsonian  Institution,  1897. 
430 


LITERATURE  43 1 

A  List  of  Works  on  North  American  Entomology.     N.  Banks.     Bull.  U.  S.  Dept.  Agric, 
Bur.  Ent.,  no.  81  (n.s.),  120  pp.     Washington,  1910. 

GENER.\L  ENTOMOLOGY 

Kirby,  W.,  and  Spence,  W.     1822-26.     An  Introduction  to  Entomology.     4  vols.     36  + 

2413  pp.,  30  pis.     London. 
Burmeister,  H.     1832-55.     Handbuch  der  Entomologie.     2  vols.     28  +  1746  pp.,  16  taf. 
Trans,  of  Band  i  :  1836.     W.  E.  Shuckard.     A  Manual  of  Entomology.     12  + 
654  pp.,  32  pis.     London. 
Westwood,  J.  O.     1839-40.     An  Introduction  to  the  Modern  Classification  of  Insects. 

2  vols.     23  +  620  pp.,  133  figs.    London. 
Graber,  V.     1877-79.     Die  Insekten.     2  vols.     8  +  1008  pp.,  404  figs.     MUnchen. 
Miall,  L.  C,  and  Denny,  A.     1886.     The  Structure  and  Life-History  of  the  Cockroach. 

6  +  224  pp.,  125  figs.     London,  Lovell  Reeve  &  Co.;  Leeds,  R.  Jackson. 
Comstock,  J.  H.     1888.     An  Introduction  to  Entomology.     4  +  234  pp.,  201  figs.     Ithaca, 

N.  Y. 
Kolbe,  H.  J.     1889-93.     Einfuhrung  in  die  Kenntnis  der  Insekten.    12  +  709  pp.,  324  figs. 

Berlin.     F.  Diimmler.* 
Packard,  A.  S.     1889.     Guide  to  the  Study  of  Insects.     Ed.  9.     12  +  715  pp.,  668  figs., 

15  pis.     New  York.     Henry  Holt  &  Co. 
Hyatt,  A.,  and  Arms,  J.  M.     1890.     Insecta.     23  +  300  pp.,  13  pis.,  223  figs.     Boston. 

D.  C.  Heath  &  Co.* 
Kirby,  W.  F.     1892.     Elementary  Text-Book  of  Entomology.     Ed.  2.    8  -t-  281  pp.,  87  pis. 

London.     Swan  Sonnenschein  &  Co. 
Comstock,  J.  H.  and  A.  B.     1895.     A  Manual  for  the  Study  of  Insects.     7  +  701  pp., 

797  figs.,  6  pis.     Ithaca,  N.  Y.     Comstock  Pub.  Co. 
Sharp,  D.     1895, 1901.     Insects.     Cambr.  Nat.  Hist.,  vols.  5,  6.     12  -f  1130  pp.,  618  figs. 

London  and  New  York.     Macmillan  &  Co.* 
Comstock,  J.  H.     1897,  1901.     Insect  Life.     6  -|-  349  PP-,  18  pis.,  296  figs.     New  York. 

D.  Appleton  &  Co. 
Packard,  A.  S.     1898.     A  Text-Book  of  Entomology.     17 -f  729  pp.,  654  figs.     New  York 

and  London.     The  Macmillan  Co.* 
Carpenter,  G.  H.     1899.     Insects;  their  Structure  and  Life.     11  +  404  pp.,   184  figs. 

London.     J.  M.  Dent  &  Co.* 
Packard,  A.  S.     1899.     Entomology  for  Beginners.     Ed.  3.     16  -f  367  pp.,  273  figs.     New 

York.     Henry  Holt  &  Co.* 
Howard,  L.  O.    1901.     The  Insect  Book.     27  -|- 429  pp.,  48  pis.,  264  figs.     New  York. 

Doubleday,  Page  &  Co. 
Hxmter,  S.J.     1902.     Elementary  Studies  in  Insect  Life.     18 -f  344  pp.,  234  figs.    Topeka. 

Crane  &  Co. 
Henneguy,    L.    F.     1904.    Les    Insectes.     Morphologic,    Reproduction,    Embryogenie. 

18  4-  804  pp.,  622  figs.,  4  pis.     Paris.     Masson  et  Cie.     Contains  more  than  two 

thousand  references.* 
Kellogg,  V.  L.     1905.     American  Insects.     7  +  674  pp.,  13  pis.,  812  figs.     New  York. 

Henry  Holt  &  Co. 
Berlese,  A.     1909-13.     Gli  Insetti.     Vol.  i,     10  +  1004  pp.,  1292  figs.,  10  pis.     Vol.  2, 

240  pp.  233  figs.     Milan.     Contains  exhaustive  bibliographies.* 
Sanderson,  E.  D.,  and  Jackson,  C.  F.     1912.     Elementary  Entomology,     5  +  372  pp., 

496  figs.     Boston  and  New  York.     Ginn  &  Co. 
Sanderson,  E.  D.,  and  Peairs,  L.  M.     1917.     School  Entomology.     7  +  356  pp.,  233  figs. 

New  York.     John  Wiley  &  Sons,  Inc. 


432  ENTOMOLOGY 

Lutz,  F.  E.     1918.     Fieldbook  of  Insects.     9  +  5C9  pp.,  101  pis.     New  York  &  London. 

G.  P.  Putman's  Sons.* 
Comstock,  J.  H.     1920.     An  Introduction  to  Entomology.     Second  Ed.      18  +  220  pp., 

220  figs.     Ithaca,  N.  Y.     Comstock  Pub.  Co.* 

PHYLOGENY  AND  CLASSIFICATION 

Kirby,  W.,  and  Spence,  W.     1822-26     An  Introduction  to  Entomologj-.     4  vols.     36  + 

2413  pp.,  30  pis.     London. 
Burmeister,  H.     1832.     Handbuch  der  Entomologie.     2  vols.     28  +  1746  pp.,   16  taf. 

Berlin.     Translation  of  Band  i  :  1836.     W.  E.  Shuckard.     A  Manual  of  Entomol- 
ogy.    12  +  654  pp.,  32  pis.     London.     Contains  useful  synopses  of  the  older 

systems  of  classification. 
Westwood,  J.  O.     1839-40.     An  Introduction  to  the  Modern  Classification  of  Insects. 

2  vols.     23  +  620  pp.,  133  figs.     London. 
Packard,  A.   S.     1873.     Our   Common   Insects.     255  pp.,   268  figs.     Boston.     Estes  & 

Lauriat. 
Lubbock,  J.     1874.     On  the  Origin  and  Metamorphoses  of  Insects.     16  +  108  pp.,  63  figs., 

6  pis.     London.     Macmillan  &  Co.* 
Mayer,    P.     1876.     Ueber    Ontogenie    und    Phylogenie    der    Insekten.     Jenais.     Zeits. 

Naturw.,  bd.  10,  pp.  125-221,  taf.  6-6c. 
Haase,  E.     1881.     Beitrag  zur  Phylogenie  und  Ontogenie  der  Chilopoden.     Zeits.     Ent. 

Breslau,  bd.  8,  heft  2,  pp.  93-115. 
Packard,  A.  S.     1881.     Scolopendrella  and  its  Position  in  Nature.     Amer.  Nat.,  vol.  15, 

pp.  698-704,  fig.  I. 
Brauer,  F.     1885.     Systematisch-zoologische  Studien.     Sitzb.    Akad.  Wiss.,  Wien,  bd.  91, 

pp.  237-413.* 
Grassi,  B.     1885.     I  progenitori  degli  Insetti  e  dei  Miriapodi. — Morfologia  delle  Scolo- 

pendreUe.     Atti.  Accad.  Torino,  t..  21,  pp.  48-50. 
Glaus,  C.     1887.     On  the  Relations  of  the  Groups  of  Arthropoda.     Ann.  Mag.  Nat.  Hist., 

ser.  5,  vol.  19,  p.  396. 
Haase,  E.     1889.     Die  Abdominalanhange  der  Insekten  mit  Beriicksichtigung  der  Myrio- 

poden.     Morph.  Jahrb.,  bd.  15,  pp.  33i-435>  taf.  14,  15. 
Femald,  H.  T.     1890.     The  Relationships  of  Arthropods.     Studies   Biol.  Lab.   Johns 

Hopk.  Univ.,  vol.  4,  pp.  431-513,  pis.  48-50. 
Hyatt,  A.,  and  Arms,  J.  M.     1890.     Insecta.     23  +  300  pp.,  13  pis,  223  figs.     Boston. 

D.  C.  Heath  &  Co.* 
Cholodkowsky,  N.     1892.     On  the  Morphology  and  Phylogeny  of  Insects.     Ann.  Mag. 

Nat.  Hist.,  ser.  6,  vol.  10,  pp.  429-451. 
Grobben,  C.     1893.    A  Contribution  to  the  Knowledge  of  the  Genealogy  and  Classification 

of  the  Crustacea.     Ann.  Mag.  Nat.  Hist.,  ser.  6,  vol.  11,  pp.  440-473.     Trans. 

from  Sitzb.  Akad.  Wiss.  Wien,  math.-nat.  CI.,  bd.  loi,  heft  2,  pp.  237-274,  taf.  i. 
Hansen,     H.     J.     1893.     A     Contribution     to     the     Morphology      of      the     Limbs 

and  Mouth-parts  of  Crustaceans  and  Insects.     Ann.    Mag.  Nat.    Hist.,    ser.    6, 

vol.  12,  pp.  417-434.     Trans,  from  Zool.  Anz.,  jhg.  16,  pp.  193-198,  201-212. 
Pocock,  R.  I.     1893.     On  some  Points  in  the  Morphology  of  the  Arachnida  (s.  s.)  with 

Notes  on  the  Classification  of  the  Group.     Ann.  Mag.  Nat.  Hist.,  ser.  6.  vol.  11, 

pp.  1-19,  pis.  I,  2. 
Bernard,  H.  M.     1894.     The  Systematic  Position  of  the  Trilobites.     Quart.  Journ.  Geol. 

Soc.  London,  vol.  50,  pp.  411-434,  figs.  1-17. 
Kenyon,  F.  C.     1895.    The  Morphology  and  Classification  of  the  Pauropoda,  with  Notes  on 

the  Morphology  of  the  Diplopoda.     Tufts  Coll.  Studies,  no.  4,  pp.  77-146,  pis. 

1-4.* 


LITERATURE 


433 


Schmidt,  P.     1896.     Beitrage  zur  Kenntnis  der  niederen  Myriapoden.     Zeits.  wiss.  Zool., 

bd.  5Q,  pp.  436-510,  taf.  26,  27. 
Wagner,  J.     1895.     Contributions  to  the  Phylogeny  of  the  Arachnida.     Ann.  Mag.  Nat. 

Hist.,  ser.  6,  vol.  15,  pp.  285-315.     Trans,  from  Jenais.  Zeits.  Naturw.,  bd.  29, 

pp.  123-156. 
Sedgwick,  A.     1895.     Peripatus.     Camb.  Nat.  Hist.,  vol.  5,  pp.  1-26,  figs.  1-14. 
Sinclair,  F.  G.     1895.     Myriapoda.     Camb.  Nat.  Hist.,  vol.  5,  pp.  27-80,  figs.  15-46. 
Sharp,  D.     1895,1901.     Insects.     Camb.  Nat.  Hist.,  vols.  5,  6.     12  +  1130  pp.,  618  figs. 

London  and  New  York.     Macmillan  &  Co.* 
Comstock,  J.  H.  and  A.  B.     1895.     A  Manual  for  the  Study  of  Insects.     7  +  70:  pp.,  797 

figs.,  6  pis.     Ithaca,  N.  Y.     Comstock  Pub.  Co. 
Heymons,  R.     1896.     Zur  Morphologic  der  Abdominalanhange  bei  den  Insecten.     Morph. 

Jahrb.,  bd.  24,  pp.  178-204,  i  taf. 
Heymons,  R.     1897.     Mittheilungen  iiber  die  Segmentierung  und  den  Korperbau  der 

IMyriopoden.     Sitzb.  Akad.  Wiss.,  Berhn,  bd.  40,  pp.  915-923,  2  figs. 
Hansen,  H.  J.,  and  Sorensen,  W.     1897.     The  Order  Palpigradi  Thor.  and  its  Relation- 
ship to  the  Arachnida.     Ent.  Tidsk.,  arg.  18,  pp.  223-240,  pi.  4. 
Packard,  A.  S.     1898.     A  Text-Book  of  Entomology.     17 -+- 729  pp.,  654  figs.     New  York 

and  London.     The  Macmillan  Co.* 
Packard,  A.  S.     1899.     Entomology  for  Beginners.     Ed.  3.     16  +  367  pp.,  273  figs.     New 

York.     Henry  Holt  &  Co.* 
Von  Zittel,  K.  A.     1900,1902.     Te.xt-Book  of  Palaeontology.     2  vols.     Trans.     C.R.East- 
man.    London  and  New  York.     Macmillan  &  Co.* 
Folsom,  J.  W.     1900.     The  Development  of  the  Mouth  Parts  of  Anurida  maritima  Guer. 

Bull.  Mus.  Comp.  Zool.,  vol.  36,  pp.  87-157,  pis.  1-8.* 
Hansen,  H.  J.     1902.     On  the  Genera  and  Species  of  the  Order  Pauropoda.     Vidensk. 

Medd.  Naturh.  Foren.  Kjobenhavn  (1901),  pp.  323-424,  pis.  1-6. 
Carpenter,  G.  H.     1903.     On  the  Relationships  between  the  Classes  of  the  Arthropoda. 

Proc.  R.  Irish  Acad.,  vol.  24,  pp.  320-360,  pi.  6.* 
Enderlein,  G.     1903.     Ueber  die  Morphologic,  Gruppierung  und  systematische  SteUung 

der  Corrodentien.     Zool.  Anz.,  bd.  26,  pp.  423-437,  4  figs. 
Hansen,  H.  J,     1903.     The  Genera  and  Species  of  the  Order  Symphyla.     Quart.  Journ. 

Micr.  Sc,  vol.  47  (n.  s.),  pp.  i-ioi,  pis.  1-7.- 
Packard,  A.  S.     1903.     Hints  on  the  Classification  of  the  Arthropoda;  the  Group,  a  Poly- 

phyletic  One.     Proc.  Amer.  Phil.  Soc,  vol.  42,  pp.  142-161. 
Lankester,  E.  R.     1904.     The  Structure  and  Classification  of  the  Arthropoda.     Quart. 

Journ.  Micr.  Sc,  vol.  47  (n.  s.),  pp.  523-582,  pi.  42.     (From  Encyc.  Brit.,  ed.  10.) 
Bomer,  C.     1904.     Zur  Systematik  der  Hexapoden.     Zool.  Anz.,  bd.  27,  pp.  511-533, 

figs.  1-4.* 
Bouvier,   E.  L.     1905,    1907.     Monographic   des   Onychophores.     Ann.    Sc.   nat.    Zool., 

ser.  9,  t.  2,  pp.  1-383,  140  figs.,  13  pis.;  t.  5,  pp.  61-318,  figs.  141-191.* 
Carpenter,  G.  H.     1905.     Notes  on  the  Segmentation  and  Phylogeny  of  the  Arthropoda, 

with  an  Account  of  the  Maxillae  in  Polyxenus  lagurus.     Quart.  Journ.  Micr.  Sc, 

vol.  49,  pt.  3,  pp.  469-491,  pi.  28.* 
Silvestri,  F.     1907.     Descrizione  di  un  novo  genere  d'insetti  apteygoti.  *^11.  Lab.  Zool. 

gen.  agr.,  vol.  i,  pp.  296-311,  18  figs. 
Handlirsch,  A.     1908.     Die  Fossilen  Insekten  und  die  Phylogenie  der  Rezenten  Formen. 

49  +  1430  pp.,  14  figs.,  51  pis.,  etc.     Leipzig.     W.  Engelmann.* 
Sedgwick,  A.     1908.     The  Distribution  and  Classification  of  the  Onychophora.     Quart. 

Journ.  Micr.  Sc,  vol.  52  (n.  s.),  pp.  379-406,  figs.  1-13.* 
Berlese,  A.     1909.     Monografia  dei  Myrientomata.     Redia,  vol.  6,  pp.  1-182,  17  pis.,  14 

figs. 


434  ENTOMOLOGY 

Pierce,  W.  D.  1909.  A  Monographic  Revision  of  the  Twisted  Winged  Insects  comprising 
the  Order  Strepsiptera  Kirby.  Bull.  U.  S.  Nat.  Mus.  No.  66,  pp.  12  +  232,  figs. 
1-3,  pis.  1-15.* 

Schepotieff,  A.  1909.  Studien  iiber  niedere  Insecten.  Zool.  Jahrb.,  Abt.  Syst.  Geogr. 
Biol.,  bd.  28,  pp.  121-138,  tab.  3-5. 

Bomer,  C.  1910.  Die  phylogenetische  Bedeutung  der  Protura.  Biol.  Zentralbl.  bd.  30, 
pp.  633-641. 

Prell,  H.  1911-12.  Beitrage  zur  Kenntniss  der  Protura.  Zool.  Anz.,  bd.  38,  pp.  185-193; 
bd.  39,  pp.  357-365;  bd.  40,  33-50- 

Rimsky-Korsakow,  M.  1911.  Ueber  die  systematische  Stellung  der  Protura  Silvestri. 
Zool.  Anz.,  bd.  37,  pp.  164-168,  i  fig. 

Comstock,  J.  H.  1912.  The  Spider  Book.  13  +  721  pp.,  770  figs.  New  York.  Double- 
day,  Page  &  Co.* 

Handlirsch,  A.  1913,  1920.  Aus  der  Geschichte  der  Entomologie.  Also  chapters  on 
literature,  technique,  taxonomy,  etc.  In  Schroder:  Handbuch  der  Entomologie, 
bd.  3,  pp.  1-116,  figs.  1-51.* 

Silvestri,  F.  1913.  Descrizione  di  un  nuovo  ordine  di  insetti.  Boll.  Lab.  Zool.  gen.  agr., 
vol.  7,  pp.  193-209,  13  figs. 

Williams,  C.  B.  1913.  A  Summary  of  the  Present  Knowledge  of  the  Protura.  Ento- 
mologist, vol.  46,  pp.   225-232,  figs.   I,   2.* 

Walker,  E.  M.     1914. .   A  New  Species  of  Orthoptera,  forming  a  New  Genus  and  Family. 

Can.  Ent.,  vol.  46,  pp.  93-99,  pi.  6. 
Banks,  N.     1915.     The  Acarina  or  Mites.     Rept.  U.  S.  Dept.  Agric,  no.  108,     153  pp., 

294  figs.* 
Brues,  C.  T.,  and  Melander,  A.  L.     1915.     Key  to  the  Families  of  North  American  Insects. 

7  -f  140  pp.,  18  pis.     Boston,  Mass.  and  Pullman,  Wash.      Pub.  by  the  authors. 
Crampton,  G.  C.     1915.     The  Thoracic  Sclerites  and  the  Systematic  Position  of  Gryllo- 

blatta  campodeiformis  Walker,  a  Remarkable  Annectent  "  Orthopteroid "  Insect. 

Ent.  News,  vol.  26,  pp.  337-350,  pi.  13. 
Crampton,  G.  C.     1916.     The  Orders  and  Relationships  of  Apterygotan  Insects.     Journ. 

N.  Y.  Ent.  Soc,  vol.  24,  pp.  267-301.* 
Crampton,  G.  C.     1917.     A  Phylogenetic  Study  of  the  Terminal  Abdominal  Segments  and 

Appendages  in  Some  Female  Apterygotan  and  Lower  Pterygotan  Insects.     Journ. 

N.  Y.  Ent.  Soc,  vol.  25,  pp.  225-237,  pis.  16,  17.* 
Crampton,  G.  C.     1917.     A  Phylogenetic  Study  of  the  Lateral  Head,  Neck  and  Prothoracic 

Regions  in  Some  Apterygota  and  Lower  Pterygota.     Ent.  News,  vol.  28,  pp. 

398-412,  pi.  27.* 
Caudell,  A.  N.     1918.     Zorotypus  hubbardi,  a  New  Species  of  the  Order  Zoraptera  from 

the  U.  S.     Can.  Ent.,vol.  50,  pp.  375-381. 
Pierce,  W.  D.     1918.     The  Comparative  Morphology  of  the  Order  Strepsiptera  together 

with  Records  and  Descriptions  of  Insects.     Proc.  U.  S.  Nat.  Mus.,  vol.  54,  pp. 

391-501,  pis.  64-78,* 
Brues,  C.  T.     1919.     The  Classification  of  Insects  on  the  Characters  of  the" Larva  and 

Pupa.     Biol.  Bull.,  vol.  37,  pp.  1-21.* 
Crampton,  G.  C.     1919.     Notes  on  the  Phylogeny  of  the  Orthoptera.     Ent.  News,  vol. 

30,  pp.  42-48;  64-72. 
Crampton,  G.  C.     1919.     The  Evolution  of  Arthropods  and  their  Relatives,  with  especial 

Reference  to  Insects.     Amer.  Nat.,  vol.  53,  pp.  143-179.* 
Crampton,  G.  C.     1919.     Notes  on  the  Ancestry  of  the  Diptera,  Hemiptera,  and  other 

Insects  related  to  the  Neuroptera.     Trans.  Ent.  Soc.  London,  pp.  93-118,  2  figs. 
Walker,  E.  M.     1919.     The  Terminal  Abdominal  Structures  of  Orthopteroid  Insects:  a 

Phylogenetic  Study.     Ann.  Ent.  Soc.  Amer.,  vol.  12,  pp.  267-326,  pis.  20-28. 


LITERATURE  435 

Caudell,  A.  N.     1920.     Zoraptera  not  an  Apterous  Order.     Proc.  Ent.  Soc.  Washington, 

vol.  22,  pp.  84-97,  pi.  6. 
Crampton,  G.  C.     1920.     Some  Anatomical  Details  of  the  Remarkable  Winged  Zorapteron. 

Zorotypus  hubbardi  Caudell,  with  Notes  on  its  Relationships.     Proc.  Ent.  Soc. 

Washington,  vol.  22,  pp.  98-106,  pi.  7. 
Crampton,  G.  C.     1920.     A  Comparison  of  the  External  Anatomy  of  the  Lower  Lepidop- 

tera  and  Trichoptera  from  the  Standpoint  of  Phylogeny.     Psyche,  vol.  27,  pp. 

23-44,  pi.  4.* 
Crampton,  G.  C.     1920.     Notes  on  the  Lines  of  Descent  of  Lower  Winged  Insects.     Psyche, 

vol.  27,  pp.  116-127,  6  figs. 
Crampton,  G.  C.     1921.     Preliminary  Note  on  the  interpretation  of  Insectan  and  Myrio- 

podan  structures  through  a  comparison  with  the  structures  of  Crustacea.     Trans. 

Ent.  Soc.  London,  pp.  340-346. 
Crampton,  G.  C.     1921.     A  Further  Comparison  of  the  Wings  of  Zoraptera,  Psocids,  and 

Aphids,  from  the  Standpoint  of  Phylogeny.     Can.  Ent.,  vol.  53,  pp.  110-117, 

pl.  3-* 
Ewing,  H.  E.     1921.     A  Second  Nearctic  Species  of  Protura,  Accrcntuliis  barbcri,  New 

Species.     Ent.  News,  vol.  32,  pp.  239-241. 
Ewing,  H.  E.     1921.     New  Genera  and  Species  of  Protura.     Proc.  Ent.  Soc.  Washington, 

vol.  23,  pp.  193-202,  pl.  16. 
Handlirsch,   A.     1921.     Philogenie   oder   Stammesgeschichte.     In    Schroder:  Handbuch 

der  Entomologie,  bd.  3,  pp.  307-368,  figs.  238-289. 
Crampton,  G.  C.     1922.     A  Comparison  of  the  First  Maxillae  of  Apterygotan  Insects  and 

Crusta,cea  from  the  Standpoint  of  Phylogeny.     Proc.  Ent.  Soc.  Washington,  vol. 

24,  pp.  65-82,  figs.  1-6,  pis.  8,  9.* 
Walker,  E.  M.     1922.     The  Terminal  Structures  of  Orthopteroid  Insects:  a  Phylogenetic 

Study.     Ann.  Ent.  Soc.  Amer.,  vol.  15,  pp.  1-76,  pis.  i-ii. 


GENERAL  ANATOMY 

De  Reatmiur,  R.  A.  F.     1734-42.     Memoires  pour  servir  a  I'histoire  des  insectes.     7  vols. 

Paris. 
Lyonet,  P.     1762.     Traite  anatomique  de  la  Chenille,  qui  ronge  le  Bois  de  Saule.     Ed.  2. 

22  +  616  pp.,  18  pis.     La  Haye. 
Straus-Durckheim,  H.     1828.     Considerations  generales  sur  I'anatomie  comparee  des 

animaux  articules,  etc.     19  +  434  PP-,  10  pis.     Paris. 
Newport,  G.     1839.     Insecta.     Todd's  Cyclopaedia  Anat.  Phys.,  vol.  2,  pp.  853-994,  figs. 

329-439- 
Viallanes,  H.     1882.     Recherches  sur  I'histologie  des  insectes.     Ann.  Sc.  nat.  ZooL,  ser.  6, 

t.  14,  pp.  1-348,  pis.  1-18. 
Miall,  L.  C,  and  Deimy,  A.     1886.     The  Structure  and  Life-history  of  the  Cockroach. 

6  +  224  pp.,  125  figs.     London,  Lovell  Reeve  &  Co.;  Leeds,  R.  Jackson. 
Schaeffer,  C.     1889.     Beitrage  zur  Histologie  der  Insekten.     Zool.  Jahrb.,  Morph.  Abth., 

bd.  3,  pp.  611-652,  taf.  29,  30. 
Lowne,  B.  T.     1890-92.     The  Anatomy,  Physiology,  Morphology  and  Development  of  the 

Blow-fly  (Calliphora  erythrocephala) .    A  Study  in  the  Comparative  Anatomy  and 

Morphology  of  Insects.     8  -f  778  pp.,  108  figs.,  21  pis.     London.* 
Lang,  A.     1891.    Text-Book  of  Comparative  Anatomy.    Trans,  by  H.  M.  and  M.  Bernard. 

Pt.  I,  pp.  438-508,  figs.  301-356.     London  and  New  York.     Macmillan  &  Co.* 
Comstock,  J.  H.,  and  Kellogg,  V.  L.     1899.     The  Elements  of  Insect  Anatomy.     Rev.  ed. 

134  pp.,  II  figs.     Ithaca,  N.  Y.     Comstock  Publishing  Co. 


436  ENTOMOLOGY 

Hewitt,  C.  G.     1907-9.     The  Structure,  Development,  and  Bionomics  of  the  House-fly, 

Musca  domesticaLinn.     Quart.  Journ.  Micr.  Sc,  vol.  51   (n.  s.),  pp.  395-448,  pis. 

22-26;  vol.  52,  pp.  495-545.  pis.  30^33;  vol.  54,  PP-  347-414,  pl-  22.* 
Snodgrass,  R.  E.     1910.     The  Anatomy  of  the  Honey  Bee.     Bull.  U.   S.  Dept.  Agr., 

Bur.  Ent.,  Tech.  Ser.  No.  18.     162  pp.,  57  figs.* 
Schroder,  C.     1912-21.     Handbuch  der  Entomologie.     Bd.  i,  3,  Lief.  1-7,  928  pp.,   716 

figs.     Jena.     Gustav  Fischer.* 
Jordan,  H.     1913.     Vergleichende  Physiologic  wirbelloser  Tiere.     Bd.  i,  pp.  22  +  738, 

277  figs.     Jena.     Gustav  Fischer.* 


HEAD  AND  APPENDAGES 

Burgess,  E.     1880.     Contributions  to  the  Anatomy  of  the  Milk-weed  Butterfly  (Danais 

archippus  Fabr.).     Anniv.  Mem.  Bost.  Soc.  Nat.  Hist.,  16  pp.,  2  pis. 
Ditnmock,  G.     1881.     The  Anatomy  of  the  Mouth  Parts  and  of  the  Sucking  Apparatus  of 

some  Diptera.     50  pp.,  4  pis.     Boston.     A.  Williams  &  Co.* 
Kraepelin,  K.     1883.     Zur  Anatomic  und  Physiologic  des  Russels  von  Musca.     Zeits.  wiss. 

Zool.,  bd.  39,  pp.  683-719,  taf.  40,  41. 
Wedde,  H,     1885.     Beitrage  zur  Kenntniss  des  Rhynchotenriissels.     Archiv  Naturg. ,  jhg. 

51,  bd.  I,  pp.  1 13-143,  taf.  6,  7. 
Walter,     A.     1885.     Beitrage     zur     Morphologic     der     SchmetterUnge.     Jenais.     Zeits. 

Naturw.,  bd.  18,  pp.  751-807,  taf.  23,  24. 
Walter,    A.     1885.     Zur    Morphologic    der    Schmettetlingsmundthcile.     Jenais.     Zeits. 

Naturw.,  bd.  19,  pp.  19-27. 
Breithaupt,   P.   F.     1886.     Uebcr   die   Anatomic   und  die  Functioncn  der  Bienenzunge. 

Archiv  Naturg.,  Jhg.  52,  bd.  i,  pp.  47-112,  taf.  4,  5.* 
Blanc,  L.     1891.     La  tete  du  Bombyx  mori  a  I'etat  larvaire,  anatomic  et  physiologic. 

Trav.  Lab.  Etud.  Soie,  1 889-1 890,  180  pp.,  95  figs.     Lyon. 
Hansen,  H.  J.     1893.     A  Contribution  to  the  Morphology  of  the  Limbs  and  Mouth  Parts 

of  Crustaceans  and  Insects.     Ann.  Mag.  Nat.  Hist.,  ser.  6,  vol.  11,  pp.  417-434. 

Trans,  from  Zool.  Anz.,  jhg.  16,  pp.  193-198,  201-212. 
Kellogg,  V.  L.     1895.     The  Mouth  Parts  of  the  Lepidoptera.     Amer.  Nat.,  vol.  29,  pp. 

546-556,  pl.  25,  figs.  I,  2. 
Folsom,  J.  W.     1899.     The  Anatomy  and  Physiology  of  the  Mouth  Parts  of  the  Collem- 

bolan,  Orchcsclla  cincta  L.     Bull.  Mus.  Comp.  Zool.,  vol.  35,  pp.  7-39,  pls.  i-4-* 
Janet,  C.     1899.     Essai  sur  la  constitution  morphologiquc  de  la  tete  dc  I'insecte.     74  pp., 

7  pis.     Paris.     G.  Carre  et  C.  Naud. 
Kellogg,  V.  L.     1899.     The  Mouth  Parts  of  the  Ncmatoccrous  Diptera.     Psyche,  vol.  8, 

pp.  303-306,  327-330,  346-348,  355-359,  363-365,  figs.  i-ii. 
Folsom,  J,  W,     1900.     The  Development  of  the  Mouth  Parts  of  Anurida  maritima  Guer. 

Bull.  Mus.  Comp.  Zool.,  vol.  36,  pp.  87-157,  pis.  1-8.* 
Comstock,  J.  H.,  and  Kochi,  C.     1902.     The  Skeleton  of  the  Head  of  Insects.     Amer. 

Nat.,  vol.  36,  pp.  13-15,  figs.  1-29.* 
Kellogg,  V.  L.     1902.     The  Development  and  Homologies  of  the  Mouth  Parts  of  Insects. 

Amer.  Nat.,  vol.  36,  pp.  683-706,  figs.  1-26. 
Meek,  W.  J.     1903.     On  the  Mouth  Parts  of  the  Hcmiptera.     Kansas  Univ.  Sc.  Bull.,  vol. 

2  (12),  pp.  257-277,  pis.  7-11.* 
Holmgren,  N.     1904.     Zur  Morphologic  des  Insektenkopfes.     Zeits.  wiss.  Zool.,  bd.  76, 

pp.  439-477,  taf.  27,  28.* 
Kulagin,  N.     1905.     Der  Kopfbau  bei  Culex  und  Anopheles.     Zeits.  wiss.  Zool.,  bd.  83, 

pp.  285-335,  taf.  12-14.* 


LITERATURE  437 

Demoll,  R.  1908.     Die  Mundteile  der  solitiiren  Apiden.     Zeits.  wiss.  Zool.,  bd.  91,  pp. 

1-5 1,  taf.  I,  2,  II  figs. 
Demoll,  R.     1909.     Die  Mundteile  der  Vespen,  etc.     Zeits.  wiss.  Zool,  bd.  92,  pp.  187-209, 

taf.  II,  9  figs. 
Wesche,  W.     1909.     The  Mouth-parts  of  the  Nemocera,  etc.     Journ.  Roy.  Micr.  Soc, 

pp.  1-16,  pis.  1-4. 
Tower,  D.  G.     1914.     The  Mechanism  of  the  Mouth  Parts  of  the  Squash  Bug,  Anasa 

tristis  De  Geer.     Psyche,  vol.  21,  pp.  99-108,  2  pis.* 
Peterson,  A.     1915.     Morphological  Studies  of  the  Head  and  Mouth  Parts  of  the  Thy- 

sanoptera.     Ann.  Ent.  Soc.  Amer.,  vol.  8,  pp.  20-59,  7  pls.* 
Peterson,  A.     1916.     The  Head-Capsule  and  Mouth-Parts  of  Diptera.     111.  Biol.  Monogr., 

vol.  3,  no.  2,  112  pp.,  25  pis.* 
Peacock,  A.  D.     1918.     The  Structure  of  the  Mouth  Parts  and  Mechanism  of  Feeding  in 

Pediculus  humanus.     Parasitology,  vol.  11,  pp.  98-117,  6  figs.,  i  pi.* 
Yuasa,  H.     1920.     The  Anatomy  of  the  Head  and  Mouth  Parts  of  Orthoptera  and  Euplex- 

optera.     Journ.  Morph.,  vol.  33,  pp.  251-307,  pis.  1-9.* 
Crampton,  G.  C.     1921.     The  Sclerites  of  the  Head,  and  the  Mouth  Parts  of  Certain. 

Immature  and  Adult  Insects.     Ann.  Ent.  Soc.  Amer.,  vol.  14,  pp.  65-103,   pis. 

2-8.* 
Crampton,  G.  C.     1921.     The  Origin  and  Homologies  of  the  So-called  "Superlinguae"  or 

"  Paraglossae "  (Paragnaths)  of  Insects  and  Related  Arthropods.     Psyche,  vol. 

28,  pp.  84-92,  pi.  5. 
Crampton,  G.  C.    1922.     The  Derivation  of  Certain  Types  of  Head  Capsule  in  Insects 

from  Crustacean  Protot>'pes,      Proc.  Ent.     Soc.  Washington,  vol.  24,  pp.  153-157, 

pi.  15. 

THORAX  AND  APPENDAGES;  LOCOMOTION 

Pettigrew,    J.   B.     1874.     Animal  Locomotion.     13  -f  264   pp.,    130   figs.     New   Yoric 

D.  Appleton  &  Co. 
Marey,  E.  J.     1874,  1879.     Animal  Mechanism.     16  +  283  pp.,  117  figs.     New  York. 

D.  Appleton  &  Co. 
Von  Lendenfeld,  R.     1881.     Der  Plug  der  Libellen.     Ein  Beitrag  zur  Anatomie  und  Phy- 

siologie  der  Flugorgane  der  Insecten.     Sitzb.  Akad.  Wiss.  Wien,  bd.  83,  pp.  289- 

376,  taf.  1-7. 
Dahl,   F.    1884.     Beitrage  zur  Kenntnis  des  Baues  und  der  Funktionen  der  Insektenbeine. 

Archiv  Naturg.,  jhg.  50,  bd.  i,  pp.  146-193,  taf.  11-13. 
Dewitz,  H.     1884.     Ueber  die  Fortbewegung  der  Thiere  an  senkrechten  glatten  Flachen 

vermittelst  eines  Sekretes.     Pfliiger's  Archiv  ges.  Phys.,  bd.  3$,  pp.  440-480,  taf. 

7-9- 
Graber,  V.     1884.     Ueber  die  Mechanik  des  Insektenkorpers.     I.  Mechanik  der  Beine. 

Biol.  Centralbl.,  bd.  4,  pp.  560-570. 
Amans,  P.     1885.     Comparaisons  des  organes  du  vol  dans  le  serie  animale.     Ann.  Sc.  nat. 

Zool.,  ser.  6,  t.  19,  pp.  1-222,  pis.  1-8. 
Redtenbacher,   J.     1886.     Vergleichende   Studien   iiber   das   Fliigelgeader   der  Insecten. 

Ann.  naturh.  Hofm.  Wien,  bd.  i,  pp.  153-232,  taf.  9-20. 
Amans,  P.  C.     1888.     Comparaisons  des  organes  de  la  locomotion  aquatique.     Ann.  Sc. 

nat.  Zool.,  ser,  7,  t.  6,  pp.  1-164,  pis.  1-6. 
Ockler,  A.     1890.     Das  Krallenglied  am  Insektenfuss.     Archiv  Naturg.,  jhg.  56,  bd.    i, 

pp.     221-262,  taf.  12,  13. 
Demoor,  J.     1891.     Recherches  sur  la  marche  des  Insectes  et  des   Arachnides.     Archiv. 

Biol.,  t.  10,  pp.  567-608,  pis.  18-20. 


438  ENTOMOLOGY 

Hoffbauer,  C.     1892.     Beitrage  zur  Kenntnis  der  Insektenfliigel.     Zeits.  wiss.  Zool.,  bd. 

54,  pp.  579-630,  taf.  26,  27,  3  figs.* 
Sptiler,  A.     1892.     Zur  Phylogenie  und  Ontogenie  des  Fliigelgeader  der  Schmetterlinge. 

Zeits.  wiss.  Zool.,  bd.  53,  pp.  597-646,  taf.  25,  26. 
Comstock,   J,   H.     1893.     Evolution   and   Taxonomy.     Wilder    Quarter-Century  Book, 

pp.  37-114,  pis.  1-3.     Ithaca,  N.  Y. 
Marey,  E.  J.     1895.     Movement.     15  +  323  pp.,  204  figs.     New  York.     D.  Appleton 

&  Co. 
Comstock,  J.  H.,  and  Needham,  J.  G.     1898-99.     The  Wings  of  Insects.    Amer.  Nat.,  vols. 

32,  ss,  pp.  43-48,  81-89,  231-257,  335-340,  413-424,  561-565,  769-777,  903-9"» 

117-126,   573-582,     845-860,    figs.    1-90.     Reprint,    Ithaca,   N.   Y.     Comstock 

Pub.  Co. 
Verhoeff,  K.  W.     1902.     Beitrage  zur  vergleichenden  Morphologic  des  Thorax  der  Insekten 

mit  Beriicksichtigung  der  Chilopoden.     Nova  Acta  Leop.-Carol.  Akad,  Naturf., 

bd.  81  pp.  63-110,  taf.  7-13. 
Woodworth,   C.  W.     1906.     The  Wing  Veins  of  Insects.     Tech.  Bull.  Ent.,  U.  of  Cal. 

A.  E.  S.,  vol.  I,  No.  I,  pp.  1-152,  figs,  i-ioi.* 
Durken,  B.     1907.     Die  Tracheenkiemenmuskulatur  der  Ephemeriden  unter  Beriicksichti- 
gung der  Morphologie  des  Insektenflugels.     Zeits.  wiss.  Zool,  bd.  87,  pp.  435-SSo, 

taf.  24-26,  30  figs.* 
Snodgrass,  R.  E.     1908.     A  Comparative  Study  of  the  Thorax  in  Orthoptera,  Euplex- 

optera  and  Coleoptera.     Proc.  Ent.  Soc.  Wash.,  vol.  9,  pp.  95-108,  pis.  2-5. 
Crampton,  G.  C.     1909.     A  Contribution  to  the  Comparative  Morphology  of  the  Thoracic 

Sclerites  of  Insects.     Proc.  Acad.  Nat.  Sc,  Phila.,  vol.  61,  pp.  3-54,  figs.  1-21,  pis. 

1-4.* 
Snodgrass,  R.  E.     1909.     The  Thorax  of  Insects  and  the  Articulation  of  the  Wings.     Proc. 

U.  S.  Nat.  Mus.,  vol.  36,  pp.  511-595,  pis.  40-69,  figs.  1-6.* 
Snodgrass,  R.  E.     1910.     The  Thorax  of  the  Hymenoptera.     Proc.  U.  S.  Nat.  Mus.,  vol. 

39,  PP-  37-91,  pis.  1-16.* 
Stellwaag,  F.     1910.     Bau  und  Mechanik  des  Flugapparates  der  Biene.     Zeits.  wiss.  Zool., 

bd.  95,  pp.  518-550,  taf.  19,  20,  figs.  1-6.* 
Ritter,  W.     1911.     The  Flying  Apparatus  of    the  Blow-fly.     Smithson.  Miscell.   Coll., 

vol.  56,  No.  12,  76  pp.,  7  figs.,  19  pis.* 
Pflugstaedt,  H.     1S12.     Die  Halteren  der  Dipteren.     Zeits.  wiss.  Zool.,  bd.  100,  pp.  1-59, 

taf.  1-4.* 
Voss,  F.     1904,  1912.     Ueber  den  Thorax  von  Gryllus  domesticus.     Zeits.  wiss.  Zool,  bd. 

78,  pp.  268-251,  23  figs.,  taf.  15,  16;  bd.  100,  pp.  589-834,  36  figs.,  taf.  19-28;  bd. 

loi,  pp.  445-682,  16  figs.,  taf.  25-29.* 
Crampton,  G.  C.     1916.     The  Phylogenetic  Origin  and  the  Nature  of  the  Wings  of  Insects 

according  to  the  Paranotal  Theory.     Journ.  N.  Y.  Ent.  Soc,  vol.  24,  pp.  1-39, 

pis.  1-2.* 
Martin,  J.  F.     1916.     The  Thoracic  and  Cervical  Sclerites  of  Insects.     Ann.  Ent.  Soc. 

Amer.,  vol.  9,  pp.  35-83,  pis.  1-4. 
Comstock,  J.  H.     1918.     The  Wings  of  Insects.     18 -f  430  pp.,  427  figs.,  10  pis.      Ithaca, 

N.  Y.     Comstock  Pub.  Co.* 
Mallock,    H.  R.  A.     1919.     Some  Points  in  Insect  Mechanics.     Proc.  Zool.  Soc.  London, 

pp.  111-116. 
Tillyard,  R.  J.     1919.     The  Panorpoid  Complex.     Part  3:— The  Wing- Venation.      Proc. 

Linn.   Soc.   New   South  Wales,   vol.   44,   pt.   3,   pp.   533-718,  figs.   35-112,  pis. 

3I--35-* 
Prochnow,  O.     1921.     Mechanik  des  Insektenfluges.     In  Schroder:  Handbuch  der  Ento- 
mologie,  bd.  i  pp.  534-560,  figs.  1-25. 


LITERATURE 


ABDOMEN  AND  APPENDAGES 


439 


Dewitz,  H.     1875.     Ueber  Bau  und  Entwickelung  des  Stachels  und  der  Legescheide  einiger 

Hymenopteren  und  der  grunen  Heuschrecke.     Zeits.  wiss.  Zool.,  bd.  25,  pp.  174- 

200,  taf.  12,  13. 
Adler,  H.     1877.     Lege-Apparat  und  Eierlegen  der  Gallwespen.     Deuts.  ent.  Zeits.,  jhg. 

21,  pp.  305-332,  taf.  2. 
Dewitz,  H.     1877.     Ueber  Bau  und  Entwickelung  des  Stachels  der  Ameisen.     Zeits.  wiss. 

Zool.,  bd.  28,  pp.  527-556,  taf.  26. 
Goossens,  T.     1887.    Les  pattes  des  Chenilles.     Ann.  Soc.  ent.  France,  s^r.  6,  t.  7,  pp. 

385-404,  pi.  7. 
Graber,  V.     1888.     Ueber  die  Polypodie  bei  Insekten-Embryonen.  '  Morph.  Jahrb.,  bd.  13, 

pp.  586-615,  taf.  25,  26. 
Haase,   E.     1889.     Ueber   Abdominalanhange    bei    Hexapoden.     Sitzb.   Gesell.    naturf. 

Freunde,  pp.  19-29. 
Haase,  E,     1889.     Die  Abdominalanhange  der  Insekten  mit  Beriicksichtigung  der  Myri- 

opoden.     Morph.  Jahrb.,  bd.  15,  pp.  331-435,  taf.  14,  15. 
Carlet,  G.     1890.     Memoire  sur  le  venin  et  I'aiguillon  de  I'abeille.     Ann.  Sc.  nat.  Zool.,  ser. 

7,  t.  9,  pp.  1-17,  pl-  I- 
Packard,  A.  S.     1890.     Notes  on  some    points  in  the  external  structure  and  phylogeny  of 

Lepidopterous  larvae.     Proc.   Bost.   Soc.   Nat.   Hist.,  vol.   25,  pp.   82-114,  pis. 

I,  2. 
Wheeler,  W.  M.     1890.     On  the  Appendages  of  the  first  abdominal  Segment  of  embryo 

Insects.     Trans.  Wis.  Acad.  Sc,  vol.  8,  pp.  87-140,  pis.  1-3.* 
Escherich,  K.      1892.     Die  biologische  Bedeutung  der  Genitalanhange  der  Insekten.  Verb. 

zool.-bot.  Ges.  Wien,  bd.  42,  pp.  225-240,  taf.  4. 
Graber.    V.     1892.     Ueber   die  morphologische  Bedeutung  der  Abdominalanhange  der 

Insekten-Embryonen.     Morph.  Jahrb.,  bd.  17,  pp.  467-482, 
Escherich,  K.     1894.     Anatomische  Studien  iiber  das  mannliche  Genital-system  der  Cole- 

opteren.     Zeits.  wiss.  Zool.,  bd.  57,  pp.  620-641,  taf.  26,  3  figs. 
Verhoeff,  C.     1894.     Vergleichende  Untersuchungen  iiber  die  Abdominalsegmente  der 

weiblichen  Hemiptera-Heteroptera  und  Homoptera.     Verb.  nat.  Ver.  Bonn,  jhg. 

50,  pp.  307-374- 
HeymoDS,  R.     1895.     Die  Segmentirung  des  Insectenkorpers.     Anh.  Abh.  Preuss.  Akad. 

"Wiss.  Berlin,  39  pp.,  i  taf. 
Heymons,  R.     1895.     Die  Embryonalentwickelung  von  Dermapteren  und  Orthopteren 

unter  besonderer  Beriicksichtigung  der  Keimblatterbildung.     136  pp.,  12  taf.,  ^^ 

figs.     Jena. 
Pejrtoureau,  S.  A.     1895.     Contribution  a  I'etude  de  la  morphologie  de  I'armure  genitale 

des  Insectes.     248  pp.,  22  pis.,  43  figs.     Paris. 
Verhoeff,  C.     1895.     Cerci  und  Styli  der  Tracheaten.     Ent.  Nachr.,  jhg.  21,  pp.  166-168. 
Heymons,  R.     1896.     Grundziige  der  Entwickelung  und  des  Korperbaues  von  Odonaten 

und  Ephemeriden.     Anh.  Abh.  Akad.  Wiss.  Berlin,  pp.  66,  2  taf. 
Heymons,  R.     1896.     Zur  Morphologie  des  Abdominalanhange  bei  den  Insekten.     Morph. 

Jahrb.,  bd.  24,  pp.  178-204,  taf.  i. 
Verhoeff,  C.     1896.     Zur  Morphologie  der  Segmentanhange  bei  Insecten  und  Myriopoden. 

Zool.  Anz.,  bd.  19,  pp.  378-383,  385-388. 
Janet,  C.     1897.    Limites  morphologiques  des  anneaux  post-cephaliques  et  Musculature 

des  anneau\  post-thoraciques  chez  la  Myrmica  rubra.     Note  16.     35  pp.,  10  figs. 

Lille. 
Verhoeff,  C.     1897.     Bemerkungen  iiber  abdominale  Korperanhange  bei  Insecten  und 

Myriopoden.     Zool.  Anz.,  bd.  20,  pp.  293-300. 


440  ENTOMOLOGY 

Janet,  C.  1898.  Aiguillon  de  la  Myrmica  rubra.  Appareil  de  fermeture  de  la  glande  a 
venin.     Note  i8.     27  pp.,  3  pis.     Paris. 

Zander,  E.  1903.  Beitrage  zur  Morphologic  der  mannlichen  Geschlechtsanhange  der 
Lepidopteren.     Zeits.  wiss.  Zool.,  bd.  74,  pp.  557-615,  taf.  29,  figs.  1-15.* 

Verhoeff,  K.  W.  1917.  Zur  vergleichenden  Morphologic  des  Abdomens  der  Colcoptcrcn, 
etc.     Zeits.  wiss.  Zool.,  bd.  117,  pp.  130-204,  12  figs.,  2  pis.* 

Crampton,  G.  C.  1918.  A  Phylogcnctic  Study  of  the  Terminal  Abdominal  Structures 
and  Genitalia  of  Male  Apterygota,  Ephemcrids,  Odonata,  Plecoptcra,  Neurop- 
tera,  Orthoptcra,  and  Their  AUies.  Bull.  Brooklyn  Ent.  Soc,  vol.  13,  pp.  49-68, 
pis.  2-7.* 

Newell,  A.  G.  1918.  The  Comparative  Morphology  of  the  Genitalia  of  Insects.  Ann. 
Ent.  Soc.  Am'er.,  vol.  11,  pp.  109-156,  pis.  4-17.* 

Crampton,  G.  C.  1920.  A  Comparison  of  the  Genitalia  of  Male  Hymenoptera,  Mecop- 
tera,  Xeuroptera,  Diptera,  Trichoptera,  Lepidoptera,  Homoptera,  and  Strepsip- 
tera,  with  Those  of  Lower  Insects.     Psyche,  vol.  27,  pp.  34-44,  pis.  2-4.* 

Crampton,  G.  C.  1920.  Remarks  on  the  Basic  Plan  of  the  Terminal  Abdominal  Struc- 
tures of  the  Males  of  Winged  Insects.     Can.  Ent.,  vol.  52,  pp.  178-183,  pi.  6. 

Crampton,  G.  C.  1921.  A  Comparison  of  the  Terminal  Abdominal  Structures  of  Insects 
and  Crustacea.     Ent.  News,  vol.  32,  pp.  257-264,  pi.  5. 

INTEGUMENT 

Candeze,   E.     1874.     Les  moyens   d'attaque   et  de  defense  chez  les  Insectes.     Bull.  Acad. 

roy.  Belgique,  ser.  2,  t.  38,  pp.  787-816. 
Chun,  C.     1876.     Ueber  den  Bau,  die  Entwickelung  und  physiologische  Bedeutung  der 

Rektaldriisen  bei  den  Insekten.    Abh.  Senckenb.  naturf.  Gesell.,  bd.  10,  pp.  27-55. 

4  taf.     Separate,  1875,  31  pp.,  4  taf.     Frankfurt  a.  M. 
Scudder,  S.  H.     1877.    Antigeny  or  Sexual  Dimorphism  in  Butterflies.    Proc.  Amer.  Acad. 

Arts  Sc,  vol.  12,  pp.  150-158. 
Forel,  A.     1878.     Der  Giftapparat  und  die  Analdriisen  der  Ameisen.     Zeits.  wiss   Zool., 

bd.  30,  supp.,  pp.  28-68,  taf.  3,  4. 
Schneider,  R.     1878.     Die  Schuppen  aus  den  verschiedenen  Fliigel-  und  Korperteilen  der 

Lepidopteren.     Zeits.  gesammt.  Naturw.,  bd.  51,  pp.  1-59. 
Scudder,  S.  H.     1881.     Butterflies;  Their  Structure,  Changes  and  Life-Histories,  with 

Special  Reference  to  American  Forms.     9+322  pp.,  201  figs.    New  York.    Henry 

Holt  &  Co. 
Klemensiewicz,  S.     1882.     Zur  naheren  Kenntniss  der  Hautdriisen  bei  den  Raupen  und 

bei  Malachius.     Verb,  zool.-bot.  Gesell.  Wien,  bd.  32,  pp.  459-474,  2  taf. 
Dimmock,  G.     1883.     The  Scales  of  Coleoptera.     Psyche,  vol.  4,  pp.  i-ii,  23-27,  43-47, 

63-71,  figs.  i-ii. 
Osten-Sacken,  C.  R.     1884.     An  Essay  on  Comparative  Chaetotaxy,  or  the  Arrangement 

of  Characteristic  Bristles  of  Diptera.     Trans.  Ent.  Soc.  London,  pp.  497-517. 
Simmermacher,  G.     1884.     Untersuchungen  iiber  Haftapparate  an  Tarsalgliedern  von 

Insekten.     Zeits.  wiss.  Zool.,  bd.  40,  pp.  481-556,  taf.  25-27,  2  figs. 
Dahl,  F.     1885.     Die  Fussdriisen  der  Insekten.     Archiv  mikr.  Anat.,  bd.  25,  pp.  236-263, 

taf.  12,  13.  — 

Witlaczil,  E.     1885.     Die  Anatomic  der  Psylliden.     Zeits.  wiss.  Zool.,  bd.  42,  pp.  569-638, 

taf.  20-22. 
Goossens,  T.     1886.     Des  chenilles  vesicantes.     Ann.  Soc.  ent.  France,  ser.  6,  t.  6,  pp. 

461-464.* 
Minot,  C.  S.     1886.     Zur  Kenntniss  der  Insektenhaut.     Archiv  mikr.  Anat.,  bd.  28,  pp. 

37-48,  taf.  7. 


LITERATURE  44 1 

Schaffer,  C.     1889.     Beitrage  zur  Histologic  der  Insekten.     Zool.   Jahrb.,  Abth.   Anat. 

Ont.,  bd.  3,  pp.  611-652,  taf.  29,  30. 
Packard,  A.  S.     1890.     Notes  on  some  points  in  the  external  structure  and  phylogeny  of 

lepidopterous  larvje.     Proc.  Bost.  Soc.  Nat.  Hist.,  vol.  25,  pp.  82-114,  pis.  i,  2. 
Borgert,  H.     1891.     Die  Hautdriisen  der  Tracheaten.     81  pp.,  taf.     Jena. 
Kellogg,  V.  L.     1894.     The  Taxonomic  Value  of  the  Scales  of  the  Lepidoptera.     Kansas 

Univ.  Quart.,  vol.  3,  pp.  45-89,  pis.  9,  10,  figs.  1-17. 
Lutz,   K.  G.     1895.    Das  Bluten  der  Coccinelliden.    Zool.  Anz.,  jhg.  18,  pp.  244-255,  i  fig. 
Packard,  A.  S.     1895-96.     The  Eversible  Repugnatorial  Scent  Glands  of  Insects.     Journ. 

N.  Y.  Ent.  Soc,  vol.  3,  pp.  1 10-127,  pl-  5;  vol.  4,  pp.  26-32.* 
Spiiler,  A.     1895.     Beitrag  zur  Kenntniss  des  feineren  Baues  und  der  Phylogenie    der 

Fliigelbedeckung  der  Schmetterlinge.     Zool.  Jahrb.,  Abth.  .\nat.  Ont.,  bd.  8,  pp. 

520-543,  taf.  36. 
Mayer,  A.  G.     1896.    The  Development  of  the  Wing  Scales  and  their  Pigment  in  Butterflies 

and  Moths.     Bull.  Mus.  Comp.  Zool.,  vol.  29,  pp.  209-236,  pis.  1-7.* 
Bordas,  L.     1897.     Description  anatomique  et  etude  histologique  des  glandes  a  venin  des 

Insectes  hymenopteres.     53  pp.,  2  pis.     Paris. 
Cuenot,  L.     1897.     Sur  la  saignee  reflexe  et  les  moyens  de  defense  de  quelques  Insectes. 

Arch.  Zool.  e.xp.,  ser.  3,  t.  4,  pp.  655-680,  4  figs. 
Hilton,  W.  A.     1902.     The  Body  Sense  Hairs  of  Lepidopterous  Larva;.     Amer.  Nat.,  vol. 

36,  pp.  561-578,  figs.  1-23.* 
Tower,  W.  L.     1902.     Observations  on  the  Structure  of  the  Exuvial  Glands  and  the  For- 
mation of  the  Exuvial  Fluid  in  Insects.     Zool.  Anz.,  bd.  25,  pp.  466-472,  figs.  1-8. 
Tower,  W.  L.     1903.     The  Development  of  the  Colors  and  Color  Patterns  of  Coleoptera, 

with  Observations  upon  the  Development  of  Color  in  Other  Orders  of  Insects. 

Univ.  Chicago,  Decenn.  Publ.,  vol.  10,  140  pp.,  3  pis. 
Plotnikow,  W.     1904.     Uber  die  Hautung  und  iiber  einige  Elemente  der  Haut  bei  den 

Insekten.     Zeits.  wiss.  Zool.,  bd.  76,  pp.  333-366,  taf.  21,  22,  2  figs. 
Kapzov,  S.     1911.     Untersuchungen  iiber  den  feineren  Bau  der  Cuticula  bei  Insekten. 

Zeits.  wiss.  Zool.,  bd.  98,  pp.  297-337,  taf.  14-16,  3  figs.* 
Deegener,  P.     1912.     Haut  und Hautorgane      In  Schroder:  Handbuch  der  Entomologie, 

bd.  I,  pp.  1-60,  figs.  1-38.* 

MUSCULAR  SYSTEM 

Lyonet,  P.     1762.     Traite  anatomique  de  la  Chenille  qui  ronge  le  Bois  de  Saule.     Ed.  2. 

22  4-  616  pp.,  18  pis.     La  Haye. 
Straus-Durckheim,  H.     1828.     Considerations  generales  sur  I'anatomie  comparee    Hes 

animaux  articules,  etc.     434  pp.,  10  pis.     Paris. 
Newport.  G.     1839.     Insecta.     Todd's  Cyclopaedia  Anat.  Phys.,  vol.  2,  pp.  853-994,  fig<;. 

329-439. 
Lubbock,  J.     1859.     On  the  Arrangement  of  the  Cutaneous  Muscles  of  the  Larva  of  Py- 

g^era  bucephala.     Trans.  Linn.  Soc.  Zool.,  vol.  22,  pp.  163-191,  2  pis. 
Plateau,  F.     1865, 1866.     Sur  la  force  musculaire  des  insectes.     Bull.  Acad.  roy.   Belgique, 

ser.  2,  t.  20,  pp.  732-757;  t.  22,  pp.  283-308. 
Lubbock,  J.     1877.     On  some  Points  in  the  Anatomy  of  Ants.     Month.  Micr.  Journ.,  vol. 

18,  pp.  121-142,  pis.  189-192. 
Lubbock,  J.     1879.     On  the  Anatomy  of  Ants.     Trans.  Linn.  Soc.  Zool.,  ser.  2,  vol.  2,  pp. 

141-154,  2  pis. 
Von  Lendenfeld,  R.     1881.     Der  Flug  der  Libellen.     Ein  Beitrag  zur  .\natomie  und  Phy- 
siologic der  Flugorgane  der  Insecten.     Sitzb.  Akad.  Wiss.  Wien,  bd.  83,  pp.  289- 

376,  taf.  1-7. 


442  ENTOMOLOGY 

Luks,  C.     1882.     Ueber  die  Brustmuskulatur  der  Insekten.     Jenais.  Zeits.  Naturw.,  bd. 

i6,  pp.  529-552,  taf.  22,  23. 
Dahl,  F.  1884.     Beitrage  zur  Kenntnis  des  Baues  und  der  Funktionen  der  Insektenbeine. 

Archiv  Naturg.,  jhg.  50,  bd.  i,  pp.  146-193,  taf.  11-13. 
Van  Gehuchten,  A.     1886.     Etude  sur  la  structure  intime  de  la  cellule  musculaire  striee. 

La  Cellule,  t.  2,  pp.  289-453,  pis.  1-6. 
Miall,  L.  C,  and  Denny,  A.     1886.     The  Structure  and  Life-history  of  the  Cockroach. 

London  and  Leeds.*     (See  pp.  71-84.) 
Kolliker,  A.     1888.     Zur  Kenntnis  der  quergestreiften  Muskelfasern.     Zeits.  wiss.  Zool., 

bd.  47,  pp.  689-710,  taf.  44,  45. 
Biitschli,  O.,  und  Schewiakoff,  W.     1891.     Ueber  den  feineren  Bau  der  quergestreiften 

Muskeln  von  Arthropoden.     Biol.  Centralb.,  bd.  11,  pp.  33-39,  figs.  1-7. 
Rollet,  A.     1891.      Ueber    die    Streifen     N.     (Nebenscheiben),     das  Sarkoplasma  und 

Contraktion  der  quergestreiften  Muskelfasern.     Archiv  mikr.  x\nat.,  bd.  37,  pp. 

654-684,  taf.  37. 
Janet,  C.     1895.     Etudes  sur  les  Fourmis,  les  Guepes  et  les  Abeilles.     Note  12.     Structure 

des  Membranes  articulaires  des  Tendons  et  des  Muscles  (Myrmica,  Camponotus, 

Vespa,  Apis).     26  pp.,  11  figs.    Limoges. 
Janet,  C.     1895.     Sur  les  Muscles  des  Fourmis,  des  Guepes  et  des  Abeilles.     Compt.  rend. 

Acad.  Sc,  t.  121,  pp.  610-613,  I  fig. 
Bauer,  A.     1910.     Die  Muskulatur  von  Dytiscus  marginalis.     Zeits.  wiss.  Zool.,  bd.  95, 

pp.  594-646,  figs.  1-19.* 
Deegener,    P.     1913.     Muskulatur    und    Endoskelett.     In    Schroder:    Handbuch    der 

Entomologie,  bd.  i,  pp.  438-465,  figs.  320-335.* 
Kielich,  J.     1918.     Beitrage  zur  Kenntnis  der  Insectenmuskeln.     Zool.  Jahrb.,  Abth. 

Anat.  Ont.,  bd.  40,  pp.  515-536,  pis.  25-26. 

NERVOUS  SYSTEM 

Newport,  G.     1832, 1834.     On  the  Nervous  System  of  the  Sphinx  Ligustri  Linn,  and  on  the 

changes  which  it  undergoes  during  a  part  of  the  Metamorphoses  of  the  Insect. 

Phil.  Trans.  Roy.  Soc.  London,  vol.  122,  pp.  383-398,  2  pis.*     Part  II      Phil. 

Trans.  Roy.  Soc.  London,  vol.  124,  pp.  389-423,  5  pis. 
Leydig,  F.     1857.    Lehrbuch  der  Histologie  des  Menschen  und  der  Thiere.     12  -1-  551  pp., 

figs.     Frankfurt. 
Flogel,  J.  H.  L.     1878.     Ueber  den  einheitlichen  Bau  des  Gehirns  in  den  verschiedenen 

Insecten-Ordnungen.     Zeits.  wiss.  Zool.,  bd.  30,  Suppl.,  pp.  556-592,  taf.  23,  24. 
Newton,  E.  T.     1879.     On  the  Brain  of  the  Cockroach,  Blatta  orientalis.     Quart.  Journ. 

Micr.  Soc,  n.  s.,  vol.  19,  pp.  340-356,  pis.  15,  16. 
Michels,  H.     1880.     Beschreibung  des  Nervensystems  von  Oryctes  nasicornis  imL^rven-, 

Puppen-  und  Kaferzustande.     Zeits.  wiss.  Zool.,  bd.  34,  pp.  641-702,  taf.  33-36. 
Packard,  A.  S.     1880.     The  Brain  of  the  Locust.     Second  Kept.  U.  S.  Ent.  Comm.,  pp. 

223-242,  pis.  9-15,  fig.  9.     Washington.* 
Koestler,   M.     1883.     Ueber  das   Eingeweidenervensystem  von   Periplaneta   orientalis. 

Zeits.  wiss.  Zool.,  bd.  39,  pp.  572-595,  taf.  34. 
Viallanes,  H.     1884-87.     Etudes  histologiques  et  organologiques  sur  les  centres  nerveux  et 

les  organes  des  sens  des  animaux  articules.     Mem.  1-5.      Ann.  Sc.  nat.  Zool., 

ser.  6,  t.  17-19;  ser.  7,  t.  2,  4;  22  pis. 
Leydig,  F.     1885.     Zelle  und  Gewebe.      Neue  Beitrage  zur  Histologie  des  Tierkorpers, 

219  pp.,  6  taf.     Bonn. 
Binet,  A.     1894.     Contribution  a  I'etude  du  system  nerveux  sous-intestinal  des  insectes. 

Journ.  Anat.  Phys.,  t.  30,  pp.  449-580,  pis.  12-15,  23  figs. 


LITERATURE  443 

Pawlovi,  M.  I.     1895.     On  the  Structure  of  the  Blood- Vessels  and  Sympathetic  Nervous 

System  of  Insects,  particularly  Orthoptera.     Works  Lab.  Zool.  Cab.  Imp.   Univ. 

Warsaw,  pp.  96  +  22,  tab.  1-6.     In  Russian. 
Holmgren,  E.     1896.     Zur  Kenntnis  des  Hauptnervensystems  der  Arthropoden.     Anat. 

Anz.,  bd.  12,  pp.  449-457,  7  figs- 
Kenyon,  F.  C.     1896.     The  Brain  of  the  Bee.     Journ.  Comp.  Neurol.,  vol.  6,  pp.  133-210, 

pis.  14-22. 
Kenyon,  F.  C.     1896.     The  meaning  and  structure  of  the  so-called  "mushroom  bodies" 

of  the  hexapod  brain.     Amer.  Nat.,  vol.  30,  pp.  643-650,  i  fig. 
Keynon,  F.  C.     1897.     The  optic  lobes  of  the  bee's  brain  in  the  light  of  recent  neurological 

methods.     Amer.  Nat.,  vol.  31,  pp.  369-376,  pi.  9- 
Deegener,  P.     1912.     Nervensystem.     In  Schroder:  Handbuch  der  Entomologie,  bd.  i, 

pp.  76-139,  figs-  39-78.* 
Thompson,  C.  B.     1913.     A  Comparative  Study  of  the  Brains  of  Three  Genera  of  Ants, 

with  Special  Reference  to  the  Mushroom  Bodies.     Journ.  Comp.  Zool.,  vol.  23, 

PP-  515-572,  40  figs-* 

SENSE  ORGANS;  SOUNDS 

Miiller,  J.     1826.     Zur  vergleichenden  Physiologic  des  Gesichtsinnes  der  Menschen  und 

der  Tiere.     462  pp.,  8  taf.     Leipzig. 
Scudder,  S.  H.     1868.     The  Songs  of  the  Grasshoppers.     Amer.  Nat.,  vol.  2,  pp.  113-120.. 

5  figs- 
Scudder,  S.  H.     1868.     Notes  on  the  Stridulation  of  Grasshoppers.      Proc.  Bost.  Soc. 

Nat.  Hist.,  vol.  11,  pp.  306-313. 
Graber,  V.     1872.     Bemerkungen  iiber  die  Gehor-  und  Stimmorgane  der  Heuschreckeh  und 

Cicaden.    Sitzb.  Akad.  Wiss.  Wien,  math.-naturw.  CI.,  bd.  66,  pp.  205-213,  2  figs. 
Paasch,  A.     1873.     Von  den  Sinnesorganen  der  Insekten  im  AUgemeinen  von  Gehor-  und 

Geruchsorganen  im  Besondern.     Archiv  Naturg.,  jhg.  39,  bd.  i,  pp.  248-275. 
Forel,  A.     1874.    Les  fourmis  de  la  Suisse.     Neue  Denks.  allg.  Schweiz.  Gesell.  Naturw., 

bd.  26,  480  pp.,  2  taf.     Separate,  1874,  4  +  457  pp.,  2  taf.     Geneve. 
Mayer,  A.  M.     1874.     Experiments  on  the  supposed  Auditory  Apparatus  of  the  Mosquito. 

Amer.  Nat.,  vol.  8,  pp.  577-592,  fig.  92. 
Graber,  V.     1876.     Die  tympanalen  Sinnesapparate   der    Orthopteren.     Denks.    Akad. 

Wiss.  Wien,  bd.  36,  pp.  1-140,  10  taf. 
Graber,  V.     1876.     Die    abdominalen  Tympanalorgane  der   Cicaden  und  Gryllodeen. 

Denks.  Akad.  Wiss.  Wien,  bd.  36,  pp.  273-296,  2  taf. 
Mayer,  P.     1877.     Der  Tonapparat  der  Cikaden.     Zeits.  wiss.  Zool.,  bd.  28,  pp.  79-92, 

3  figs. 
Lowne,  B.  T.     1878.     On  the  Modifications  of  the  Simple  and  Compound  Eyes  of  Insects. 

Phil.  Trans.  Roy.  Soc.  London,  vol.  169,  pp.  577-602,  pis.  52-54. 
Grenacher,  H.     1879.     Untersuchungen  iiber  das  Sehorgan  der  Arthropoden,  insbesondere 

der  Spinnen,  Insekten  und  Crustaceen.     8  +  188  pp.,  11  taf.     Gottingen. 
Hauser,  G.     1880.     Physiologische  und  histiologische  Untersuchungen  uber  das  Geruchs- 

organ  der  Insekten.     Zeits.  wiss.  Zool.,  bd.  34,  pp.  367-403,  taf.  17-19. 
Graber,  V.     1882.     Die  chordotonalen  Sinnesorgane  und  das  Gehor  der  Insecten.     Archiv 

mikr.  Anat.,  bd.  20,  pp.  506-640,  taf.  30-35,  6  figs.;  bd.  21,  pp.  65-145,  4  figs.* 
Lubbock,  J.     1882.     Ants,  Bees  and  Wasps.     19  +  448  pp-,  5  pls-,  31  figs-    London. 

1884,  1901,  New  York.     D.  Appleton  &  Co. 
Graber,  V.     1883.     Fundamentalversuche  iiber  die  Helligkeits-  und  Farbenempfindlichkeit 

augenloser  und  geblendeter  Tiere.     Sitzb.  Akad.  Wiss.  Wien,  bd.  87,  pp.  201-236. 
Graber,  V.     1884.     GrundUnien  zur  Erforschung  des  Helligkeits  und  Farbensinnes  der 

Tiere.     8-1-322  pp.     Prag  und  Leipzig. 


444  ENTOMOLOGY 

Lee,  A.  B.     1884.     Bemerkungen  iiber  den  feineren  Bau  der  Chordotonal-Organe.     Archiv 

mikr.  Anat.,  bd.  23,  pp.  133-140,  taf.  7b. 
Lowne,  B.  T.     1884.     On  the  Compound  Vision  and  the  Morphology  of  the  Eye  in  Insects. 

Trans.  Linn.  Soc.  Zool.,  vol.  2,  pp.  389-420,  pis.  40-43. 
Carriere,  J.     1885.     Die  Sehorgane  der  Thiere,  vergleichend  anatomischdargestellt.    6  + 

205  pp.,  I  taf.,  147  figs.     Miinchen  und  Leipzig.     R.  Oldenbourg. 
Hickson,  S.  J.     1885.     The  Eye  and  Optic  Tract  of  Insects.     Quart.  Journ.  Micr.  Sc,  vol. 

25,  pp.  215-251,  pis.  15-17. 
Plateau,  F.     1885-88.     Recherches  experimentales  sur  la  vision  chez  les  Insectes.     Bull. 

Acad.  roy.  Belgique,  ser,  3,  t.  10,  14,  15,  16.     Mem.  Acad,  roy.  Belgique,  t.  43,  pp. 

1-9 1. 
Will,  F.     1885.     Das  Geschmacksorganderlnsekten.     Zeits.  wiss.  Zool.,  bd.  42.,  pp.  674- 

707,  taf.  27. 
Forel,  A.     1886-87.     Experiences  et  remarques  critiques  sur  les  sensations  des  Insectes. 

Rec.  zool.  Suisse,  t.  4,  pp.  1-50,  145-240,  pi.  i. 
Mark,  E.  L.     1887.     Simple  Eyes  in  Arthropods.     Bull.  Mus.  Comp.  Zool.,  vol.  13,  pp.  49- 

105,  pis.  1-5. 
Patten,  W.     1887,    1888.     Studies   on   the  Eyes  of  Arthropods.     I.   Development  of  the 

Eyes  of  Vespa,  with  Observations  on  the  Ocelli  of  some  Insects.     Journ.  Morph., 

vol.  I,  pp.  193-226,  I  pi.     II.  Eyes  of  Acilius.     Journ.  Morph.,  vol.  2^  pp.  97-190, 

pis.  7-13. 
Lubbock,  J.     1888,  1902.     On  the  Senses,  Instincts  and  Intelligence  of  Animals,  with 

Special  Reference  to  Insects.     29  +  292  pp.,  118  figs.     New  York.     D.  Appleton 

&Co. 
Vom  Rath,  O.     1888.     Ueber  die  Hautsinnesorgane  der  Insekten.     Zeits.  wiss.  Zool.,  bd. 

46,  pp.  413-454,  taf.  30,  31. 
Ruland,  F.     1888.     Beitrage  zur  Kenntnis  der  antennalen  Sinnesorgane  der  Insekten. 

Zeits.  wiss.  Zool.,  bd.  46,  pp.  602-628,  taf.  37. 
Lowne,  B.  T.     1889.     On  the  Structure  of  the  Retina  of  the  Blowfly  (Calliphora  erythro- 

cephala).     Journ.  Linn.  Soc.  Zool.,  vol.  20,  pp.  406-417,  pi.  27. 
Packard,  A.  S.     1889.     Notes  on  the  Epipharynx,  and  the  Epipharyngeal  Organs  of  Taste 

in  Mandibulate  Insects.     Psyche,  vol.  5,  pp.  193-199,  222-228. 
Pankrath,  O.     1890.     Das  Auge  der  Raupen  und  Phryganidenlarven.     Zeits.  wiss.  Zool., 

bd.  49,  PP-  690-708,  taf.  34,  35. 
Stefanowska,  M.     1890.     La  disposition  histologique  du  pigment  dans  les  yeux  des  Arthro- 

podes  sous  I'influence  de  la  lumiere  directe  et  de  I'obscurite  complete.     Rec.  zool. 

Suisse,  t.  5,  pp.  151-200,  pis.  8,  9. 
Watase,  S.     1890.     On  the  Morphology  of  the  Compound  Eyes  of  Arthropods.     Studies 

Biol.  Lab.  Johns  Hopk.  Univ.,  vol.  4,  pp.  287-334,  pis.  29-35. 
Weinland,  E.     1890.     Ueber  die  Schwinger  (Halteren)  der  Dipteren.     Zeits.  wiss.  Zool., 

bd.  51,  pp.  55-166,  taf.  7-11. 
Exner,  S.     1891.     Die  Physiologic  der  fazettierten  Augen  von  Krebsen  und  Insekten. 

8  +  206  pp.,  8  taf.,  23  figs.     Leipzig  und  Wien. 
Von  Adelung,  N.     1892.     Beitrage  zur  Kenntnis  des  tibialen  Gehorapparates  der  Locusti- 

den.     Zeits.  wiss.  Zool.,  bd.  54,  pp.  316-349,  taf.  14,  15. 
Nagel,  W.     1892.     Die  niederen  Sinne  der  Insekten.     68  pp.,  19  figs.     Tubingen. 
Child,  C.  M.     1894.     Ein  bisher  wenig  beachtetes  antennales  Sinnesorgan  der  Insekten, 

mit  besonderer  Beriicksichtigung  der  Culiciden  und  Chironomiden.     Zeits.  wiss. 

Zool,  bd.  58,  pp.  475-528,  taf.  30,  31. 
Mallock,  A.     1894.     Insect  Sight  and  the  Defining  Power  of  Composite  Eyes.     Proc.  Roy. 

Soc.  London,  vol.  55,  pp.  85-90,  figs.  1-3. 


LITERATURE  445 

Vom  Rath,  O.     1896.     Zur  Kenntnis  der  Hautsinnesorgane  und  des  scnsiblen  Nerven- 

systems  der  Arthropoden.     Zeits.  wiss.  Zool.,  bd.  61,  pp.  499-539,  taf.  23,  24. 
Redikorzew,  W.     1900.     Untersuchungen  uber  den  Bau  der  Ocellen  der  Insekten.     Zeits. 

wiss.  Zool.,  bd.  68,  pp.  581-624,  taf.  39,  40,  figs.  1-7. 
Reuter,  E.  1896.     Ueber  die  Palpen  der  Rhopaloceren,  etc.     Acta  See.  Sc.  Fenn.,  t.  22, 

pp.  16  4-  578,  6  tab. 
Hesse,  R.     1901.     Untersuchungen  uber  die  Organe  der  Lichtempfindung  bei  niederen 

Thieren.     VII.  Von  den  Arthropoden- Augen.     Zeits.  wiss.  Zool.,  bd.  70,  pp.  347- 

473,  taf.  16-21,  figs.  I,  2. 
Schenk,  O.     1903.     Die  antennalen  Hautsinnesorgane  einiger  Lepidoptcren  und  Hymen- 

opteren   mit   besonderer   Beriicksichtigung   der   sexuellen   Unterschiede.     Zool. 

Jahrb.,  Abth.  Anat.  Ont.,  bd.  17,  pp.  573-618,  taf.  21,  22,  4  figs.* 
Shull.A.F.     1907.     TheStridulationof  the  Snowy  Tree-cricket  ((Ecanthusniveus).     Can. 

Ent.,  vol.  39,  pp.  213-225,  figs.  14,  15.* 
Forel,  A.     1908.     The  Senses  of  Insects.     Trans,  by  M.  Yearsley.     14  +  324  pp.,  2  pis. 

London.     Methucn  &  Co.* 
Dietrich,  W.     1909.     Die  Facettenaugen  der  Dipteren.     Zeits.  wiss.  Zool.,  bd.  92,  pp. 

465-539,  taf.  22-25,  17  figs.* 
Link,  £.     1909.     Ueber  die  Stirnaugen  der  Neuropteren  und  Lepidopteren.     Zool.  Jahrb., 

Abt.  Anat.  Ont.,  bd.  27,  pp.  213-242,  taf.  15-17,  5  figs.* 
Link,  E.     1909.     Ueber  die  Stirnaugen  der  hemimetabolen  Insecten.     Zool.  Jahrb.,  Abt. 

Anat.  Ont  ,  bd.  27,  pp.  281-376,  taf.  21-24,  i4  figs.* 
Lovell,  J.  H.     1910,  1912.     The  Color  Sense  of  the  Honey  Bee.     Amer.  Nat.,  vol.  44,  pp. 

673-692;  vol.  46,  pp.  83-107. 
Turner,  C.  H.     1910.     Experiments  on  Color-vision  of  the  Honey-bee.     Biol.  Bull.,  vol.  19, 

pp.  257-279,  3  figs. 
Allard,  H.  A.     1911.     Studying  the  Stridulations  of  Orthoptera.     Proc.  Ent.  Soc.  Wash., 

vol.  13,  pp.  141-148. 
Schon,  A.    1911.     Bau  und  Entwicklung  des  tibialen  Chordotonalorgans  bei  der  Honigbiene 

und  bei  Ameisen.     Zool.  Jahrb.,  Abt.  Anat.  Ont.,  bd.  31,  pp.  439-472,  taf.  17-19, 

9  figs.* 
DemoU,  R.,  and  Scheuring,  L.     1912.     Die  Bedeutung  der  Ocellen  der  Insecten.     Zool. 

Jahrb.,  Abt.  Allg.  Zool.  Phys.,  bd.  31,  pp.  519-628,  23  figs.* 
Giinther,  K.     1912.     Die  Sehorgane  der  Larve  und  Imago  von  Dytiscus  marginalis.     Zeits. 

wiss.  Zool.,  bd.  100,  pp.  60-115,  36  figs.* 
Hochreuther,  P.     1912.     Die  Hautsinnesorgane  von  Dytiscus-margina'.is  L.,  ihr  Bau  und 

ihre  Verbreitung  am  Korper.     Zeits.  wiss.  Zool.,  bd.  103,  pp.  1-114,  102  figs.* 
Prochnow,    O.     1912.     Die   Organe   zur  Lautausserung.     In    Schroder:  Handbuch   der 

Entomologie.,  bd.  i,  pp.  61-75,  figs.  1-12.* 
Deegener,  O.     1912-13.     Sinnesorgane.     In  Schroder:  Handbuch  der  Entomologie,  bd. 

I,  pp.  140-233,  figs-  79-152.* 
Caesar,  C.  J.     1913.     Die  Stirnaugen  der  Ameisen.     Zool.  Jahrb.,  Abt.  Anat.  Ont.,  bd. 

35,  pp.  161-240,  taf.  7-10,  29  figs.* 
Jorschke,  H.     1914,     Die  Facettenaugen  der  Orthopteren   und  Termiten.     Zeits.  wiss. 

Zool.,  bd.  Ill,  pp.  153-280,  figs.  1-57,  pi.  4* 
Mclndoo,  N.  E.     1914.     The  Olfactory  Sense  of  the  Honey  Bee.     Journ.  Exp.  Zool.,  vol. 

16,  pp.  265-346,  24  figs.* 
Mclndoo,  N.  E.     1914.     The  Olfactory  Sense  of  Hymenoptera.     Proc.  Acad.  Nat.  Sc, 

pp.  294-341,  3  figs.,  pis.  II,  12.* 
Mclndoo,  N.  E.     1914.     The  Scent-producing  Organ  of  the  Honey  Bee.     Proc.  Acad. 

Nat.  Sc,  pp.  542-555,  I  fig.,  pis.  19,  20.* 


446  ENTOMOLOGY 

Mclndoo,  N.  E.     1914.     The  Olfactory  Sense  of  Insects.     Smithson.  Misc.  Coll.,  vol.  63, 

no.  9,  pp.  1-63,  figs.  1-6.* 
Mclndoo,  N.  E.     1915.     The  Olfactory  Sense  of  Coleoptera.     Biol.  Bull.,  vol.   28,  pp. 

407-460,  2  pis.* 
Mclndoo,  N.  E.     1916.     The  Sense  Organs  on  the  Mouth  Parts  of  the  Honey  Bee.     Smith- 
son.  Misc.  Coll.,  vol.  65,  no.  14,  55  pp.,  10  figs.* 
Demoll,  R.     1917.     Die  Sinnesorgane  der  Arthropoden,  ihr  Ban  und  ihre  Funktion.     243 

pp.  Braunschweig. 
Mclndoo,  N.  E.     1917.     The  Olfactory  Organs  of  Lepidoptera.     Journ.  Morph.,  vol.  29, 

PP-  33-54,  10  figs.* 
Mclndoo,  N.  E.     1918.     The  Olfactory  Organs  of  a  Coleopterous  Larva.     Journ.  Morph., 

vol.  31,  pp.  1 13-13 1,  33  figs-* 
Mclndoo,  N.  E.     1918.     The  Olfactory  Organs  of  Diptera.     Journ.  Comp.  Neur.,  vol.  29, 

pp.  457-484,  55  figs.* 
Mclndoo,  N.  E.     1919.     The  Olfactory  Sense  of  Lepidopterous  Larvae.     Ann.  Ent.  Soc. 

Amer.,  vol.  12,  pp.  65-84,  figs.  1-53-* 
Eltrihgham,  H.     1919. .  Butterfly  Vision.     Trans.  Ent.  Soc.  London,  pp.  1-49,  pis.  1-5. 
Ast,   F.     1920.     Ueber   den   feineren   Bau   der   Facettenaugen   bei   Neuropteren.     Zool. 

Jahrb.,  Abth.  Anat.  Ont.,  bd.  41,  pp.  411-458,  taf.  26-33.* 
Mclndoo,  N.  E.     1920.     The  Olfactory  Sense  of  Orthoptera.     Journ.  Comp.  Neur.,  vol. 

31,  pp.  405-427,  92  figs.* 

DIGESTIVE  SYSTEM 

Fabre,  J.  L.     1862.     Etude  sur  le  r6le  du  tissu  adipeux  dans  la  secretion  urinaire  chez  les 

Insectes.     Ann.  Sc.  nat.  Zool.,  ser.  4,  t.  19,  pp.  351-382. 
Plateau,  F.     1874,     Recherches  sur  les  phenomenes  de  la  digestion  chez  les  Insectes.  Mem. 

Acad,  ro}^  Belgique,  t.  41,  124  pp.,  3  pis. 
De  Bellesme,  J.     1876.     Physiologic  comparee.     Recherches  experimentales  sur  la  diges- 
tion des  insectes  et  en  particulier  de  la  blatte.     7  +  96  pp.,  3  pis.     Paris. 
Helm,  F.  E.     1876.     Ueber  die  Spinndriisen  der  Lepidopteren.     Zeits.  wiss.  Zool.,  bd.  26, 

pp.  434-469,  taf.  27,  28. 
Plateau,  F.     1877.     Note  additionelle  au  Memoire  sur  les  phenomenes  de  la  digestion  chez 

les  Insectes.     Bull.  Acad.  roy.  Belgique,  ser.  2,  t.  44,  pp.  710-733. 
Wilde,  K.  F.     1877.     Untersuchungen  iiber  den  Kaumagen  der  Orthopteren.     Archiv 

Naturg.,  jhg.  43,  bd.  i,  pp.  135-172,  3  taf. 
De   Bellesme,    J.     1878.     Travaux    originaux    de    Physiologie    comparee.     I.  Insectes. 

Digestion,  Metamorphoses.     252  pp.,  5  pis.     Paris. 
Schindler,  E.     1878.     Beitrage  zur  Kenntniss  der  Malpighi'schen  Gefasse  der  Insecten 

Zeits.  wiss.  Zool.,  bd.  30,  pp.  587-660,  taf.  38-40. 
Frenzel,  J.     1882.     Ueber  Bau  und  Thatigkeit  des  Verdauungskanals  derLarve  des  Tene- 

brio  moUtor  mit  Beriicksichtigung  anderer  Arthropoden.     Berl.  ent    Zeits.,  bd. 

26,  pp.  267-316,  taf.  5.* 
Leydig,  F.     1883.     Untersuchungen  zur  Anatomic  und  Histologic  der  Thiere.     174  pp., 

8  taf.     Bonn. 
MetschnikoflF,  E.     1883.     Untersuchungen  iiber  die  intrazeUulare  Verdauung  bei  wirbel- 

losen  Tieren.     Arb.  .zool.  Inst.  Wien,  bd.  5,  pp.  141-168,  2  taf. 
Schiemenz,  P.     1883.     Ueber  das  Herkommen  des  Futtersaftes  und  die  Speicheldriisen 

der  Biene  nebst  cinen  Anhangc  iiber  das  Reichorgan.     Zeits.  wiss.  Zool.,  bd.  38, 

pp.  71-135,  taf.  5-7. 
Locy,  W.  A.     1884.     Anatomy  and  Physiology  of  the  family  Nepidae.     Amer.  Nat.,  vol.  18, 

pp.  250-255,  353-367,  pis.  9-12. 


LITERATURE  447 

Witlaczil,  E.     1885.     Zur  ISlorphologie  unci  Anatomie  der  Cocciden.     Zeits.  wiss.  Zool., 

bd.  43,  PP-  149-174,  taf.  5. 
Frenzel,  J.     1886.     Einigesiiber  den  Mitteldarm  derlnsekten,  so\\ae  iiber  Epithelregenera- 

tion.     Archiv  mikr.  Anat.,  bd.  26,  pp.  229-306,  taf.  7-9. 
Kniippel,  A.     1886.     Ueber  Speicheldriisen  von  Insecten.     Archiv  Naturg.,  jhg.  52,  bd.  i, 

pp.  269-303,  taf.  13,  14. 
Cholodkovsky,  N.     1887.     Sur  la  morphologic  de  I'appareil  urinaire  des  Lepidopteres. 

Archiv.  Biol.,  t.  6,  pp.  497-514,  pi.  17. 
Faussek,  V.     1887.     Beitrage  zur  Histologic  dcs  Darmkanals  dcr  Insekten.     Zcits.  wiss. 

Zool.,  bd,  45,  pp.  694-712,  taf.  36. 
Blanc,  L.     1889.     Etude  sur  la  secretion  de  la  soie  et  sur  la  structure  du  brin  ct  de  la  have 

dans  Ic  Bombyx  mori.     56  pp.,  4  pis.     Lyon. 
Kowalevsky,  A.     1889.     Ein  Beitrag  zur  Kenntnis  dcr  Exkretionsorgane.     Biol.  Ccntralb., 

bd.  9,  pp.  33-47-  65-76,  127-128. 
Van  Gehuchten,  A.     1890.     Recherches  histologiques  sur  I'appareil  digestif  de  la  larve  de 

la  Ptychoptera  contaminata,  I  Part.     Etude  du  revetement  epithelial  et  recher- 
ches sur  la  secretion.     La  Cellule,  t.  6,  pp.  183-291,  pis.  1-6. 
Gilson,  G.     1890,  1893.     Recherches  sur  les  cellules  secretantcs.    La  soie  et  les  appareils 

sericigenes.     I.  Lepidopteres;  II.  Trichopteres,    La  Cellule,  t.  6,  pp.  115-182,  pis. 

1-3;  t.  10,  pp.  37-63,  pl-  4- 
Blanc,  L.     1891.     La  tete  du  Bomby.x  mori  a  I'etat  larvaire,  anatomie  et  physiologic. 

Trav.  Lab.  Etud.  Soie,  1889-1890,  180  pp.,  95  figs.     Lyon. 
Wheeler,  W.  M.     1893.     The  primitive  number  of  Malpighian  vessels  in  Insects.     Psyche, 

vol.  6,  pp.  457-460,  485-486, 497-498,  509-510,  539-541,  545-547,  561-564. 
Bordas,  L.     1895.     Appareil  glandulairc  des  Hymenopteres.     (Glandcs  salivaires,  tube 

digestif,  tubes  de  Malpighi  et  glandcs  venimeuses.)  362  pp.,  11  pis.     Paris. 
Cuenot,   L.     1895.     Etudes   physiologiques   sur  les  Orthopteres.     Arch.  Biol.,  t.  14,  pp. 

293-341,  pis.  12,  13. 
Bordas,  L.     1897.     L'appareil  digestif  dcs  Orthopteres.     Ann.  Sc.  nat.  Zool.,  ser.  8,  t.  5,  pp. 

1-208,  pis.  1-12. 
Needham,  J.  C.     1897.     The  digestive  epithehum  of  dragon  fly  nymphs.     Zool.  Bull.,  vol. 

I,  pp.  103-113,  figs.  i-io. 
Folsom,  J.  W.,  and  Welles,  M.  U.       1906.     Epithelial  Degeneration,  Regeneration,  and 

Secretion  in  the  Mid-intestine  of  CoUcmbola.     Univ.  111.  Bull.,  The  Univ.  Studies, 

vol.2,  no.  2,  pp.  1-40,  pis.  1-9. 
Deegener,  P.     1913.     Der  Darmtraktus  und  seine  Anhange.     In  Schroder:  Handbuch  der 

Entomologie,  bd.  i,  pp.  234-315,  figs.  153-211.* 


CIRCULATORY  SYSTEM 

Graber,  V.     1873.     Ueber  den  propulsatorischen  Apparat  der  Insekten.     Archiv  mikr. 

Anat.,  bd.  9,  pp.  129-196,  3  taf. 
Graber,  V.     1873.     Ueber  die  Blutkorperchen  der  Insekten.     Sitzb.  Akad.  Wiss.  Wien, 

math.-naturw.  CI.,  bd.  64  (1871),  pp.  9-44. 
Graber,  V.    1876.    Ueber  den  pulsierendenBauchsinus  dcr  Insekten.    Archiv  mikr.  Anat., 

bd.  12,  pp.  575-582,  I  taf. 
Dogiel,  J.     1877.     Anatomie  und  Physiologic  des  Herzens  der  Larve  von  Corethra  plumi- 

cornis.     Mem.     Acad.  St.  Petersburg,  ser.  7,  t.   24,  37  pp.,   2  pis.     Separate, 

Leipzig.     Voss. 
Vayssiere,  A.     1882.     Recherches  sur  I'organisation  des  larves  des  Ephemerines.     Ann.  Sc. 

nat.  Zool.,  ser.  6,  t.  13,  pp.  1-137,  pis.  i-ii. 


448  ENTOMOLOGY 

Viallanes,  H.  1882.  Recherches  sur  I'histologie  des  Insectes,  et  sur  les  phenomenes  histo- 
logiques  qui  accompagnent  le  developpement  post-embryonnaire  de  ces  animaux. 
Ann.  Sc.  nat.  ZooL,  ser,  6,  t.  14,  PP-  X-34S,  4  pls.  Bibl.  Ecole,  bd.  26,  348  pp., 
18  pis. 

Von  Wielowiejski,  H.  R.     1886.     Ueber  das  Blutgewebe  der  Insekten.     Zeits.  wiss.  Zool., 

bd.  43,  PP-  512-536.  J        r^,-    . 

Dewitz,  H.     1889.     Eigenthatige  Schwimmbewegung  der  Blutkorperchen  der    Glieder- 

thiere.     Zool.  Anz.,  jhg.  12,  pp.  457-464,  i  fig- 
Kowalevsky,  A.     1889.     Ein  Beitrag  zur  Kenntnis  der  Excretionsorgane.     Biol.  Centralb., 

bd.  9,  pp.  33-47,  65-76,  127-128. 
Schaffer,  C.     1889.     Beitrage  zur  Histologie  der  Insekten.     II.  Ueber  Blutbildungsherde 

bei  Insektenlarven.     Zool.  Jahrb.,  Abth.  Anat.  Ont.,  bd.  3,  pp.  626-636,  taf.  30. 
Pawlowa,  M.     1895.     Ueber  ampuUenartige  Blutcirculationsorgane  im  Kopfe  verschiedener 

Orthopteren.     Zool.  Anz.,  jhg.  18,  pp.  7-13,  i  fig. 
Deegener,  P.      1913.     Zirkulationsorgane  und  Leibeshohle.     In  Schroder:  Handbuch  der 
'     Entomologie,  bd.  i,  pp.  383-437,  figs-  275-319- 

FAT  BODY 

Gadeau  de  Kerville,  H.    1881, 1887.    Les   insectes   phosphorescents.     T.  i,  55  pp.,  4  pls-'. 

t.  2,  135  pp.     Rouen.* 
Von  Wielowiejski,  H.  R.     1882.     Studien  uber  Lampyriden.     Zeits.  wiss.  Zool.,  bd.  37; 

pp.  354-428,  taf.  23,  24.  _ 

Von  Wielowiejski,  H.     1883.     Ueber  den  Fettkorper  von  Corethra  plumicornis  und  seine 

Entwicklung.     Zool.  Anz.,  jhg.  6,  pp.  318-322. 
Emery,  C.     1884.     Untersuchungen  liber  Luciola  italica  L.     Zeits.  wiss.  Zool.,  bd.  40,  PP- 

338-355,  taf.  19. 
Dubois,  R.     1886.     Contribution  a  I'etude  de  la  production  de  la  lumiere  par  les  etres 

vivants.-    Les  Elaterides  lumineux.     Bull.  Soc.  zool.  France,  ann.  ix,  pp.  1-275, 

pls.  1-9. 
Heinemann    C.      1886.     Zur  .\natomie  und  Physiologic  der  Leuchtorgane  mexikanischer 

Cucuj'o's.     Archiv  mikr.  Anat.,  bd.  27,  pp.  296-382. 
Von  Wielowiejski,  H.  R.     1886.     Ueber  das  Blutgewebe  der  Insekten.     Zeits.  wiss.  Zool., 

bd.  43,  PP-  512-536.  ,      ^,     ,-,j         ^    J 

Schaflfer,   C.     1889.     Beitrage  zur  Histologie  der  Insekten.     III.  Ueber  Blutbildungsherde 

bei  Insektenlarven.     Zool.  Jahrb.,   Abth.  Anat.  Ont.,  bd.  3,  pp.  626-636,  taf.  30. 
Von  Wielowiejski,  H.  R.     1889.     Beitrage  zur  Kenntnis  der  Leuchtorgane  der  Insecten. 

Zool.  Anz.,  jhg.  12,  pp.  594-600. 
Wheeler,  W.  M,     1892.     Concerning  the  "blood  tissue"  of  the  Insecta.     Psyche,  vol.  6, 

pp.  216-220,  233-236,  253-258,  pi.  7. 
Cuenot,  L.     1895.     Etudes  physiologiques   sur   les  Orthopteres.     Arch.  Biol.,  t.  14,  pp. 

293-341,  pls.  12,  i^. 
Schmidt,  P.     1895.     On  the  Luminosity  of  Midges  (Chironomidae).     x\nn.  Mag.  Nat.  Hist., 

ser.  6,  vol.  15,  pp.  133-141-     Trans,  from  Zool.  Jahrb.,  Abth.  Syst.,  etc.,  bd.  8,  pp. 

58-66,  1894. 
Bruntz,  L.     1904.     Contribution  a  I'Etude  de  I'excretion  chez  les  Arthropodes.     Archiv. 

Biol.,  t.  20,  pp.  217-420,  pls.  7-9. 
Townsend,  A.  B.     1904.     The  Histology  of  the  Light  Organs  of  Photinus   margineUus. 

Amer.  Nat.,  vol.  38,  pp.  127-151,  figs,  i-ii.* 
Lund,  E.  J.     1911.     On  the  Structure,  Physiology  and  Use  of  Photogenic  Organs.     Journ. 

Exp.  Zool.,  vol.  II,  PP-  415-461,  pls-  1-3;  figs-  1,2.* 


LITERATURE  449 

McDermott,  F.  A.     1911.     Some  Further  Observations  on  the  Light  Emission  of  American 

Lampyrida".     Can.  Knt.,  vol.  43,  pp.  399-406. 
Coblentz,  W.  W.     1912.     A  Physical  Study  of  the  Firefly.     Publ.  No.  164,  Carnegie  Inst., 

Wash.,  47  pp.,  14  figs.,  I  pi.* 
Glaser,  R.  W.     1912.     A  Contribution  to  Our  Knowledge  of  the  Function  of  the  (Enocytes 

of  Insects.     Biol.  Bull.,  vol.  23,  pp.  213-224.* 
McDermott,  F.  A.     1912.     Recent  Advances  in  Our  Knowledge  of  the  Production  of  Light 

in  Living  Organisms.     Rept.  Smithson.  Inst.  191 1,  pp.  345-362.* 

RESPIRATORY  SYSTEM 

Dufour,  L.     1852.     Ktudes  anatomiques  et  physiologiques  et  observations  sur  les  larves  des 

Libellules.     Ann.  Sc.  nat.  Zool.,  ser.  3,  t.  17,  pp.  65-110,  3  pis. 
Williams,  T.     1853-57.     On  the  Mechanism  of  Aquatic  Respiration  and  on  the  Structure 

of  the  Organs  of  Breathing  in  Invertebrate  Animals.     Trans.  Ann.  Mag.  Nat. 

Hist.,  ser.  2,  vols.  12-19,  17  pis. 
Rathke,  H.     1861.     Anatomisch-physiologische  Untersuchungen  uber  den  Athmungspro- 

cess   der   Insecten.     Schrift,   phys.-oek.  Gesell.  Konigsberg,  jhg.  i,  pp.  99-138, 

taf.  I. 
Landois,  H.,  und  Thelen,  W.     1867.     Der  Tracheenverschluss  bei  den  Insekten.     Zeits. 

wiss.  Zool.,  bd.  17,  pp.  187-214,  I  taf. 
Gerstacker,  A.     1874.     Ueber  das  Vorkommen  von  Tracheenkiemen  bei  ausgebildeten 

Insecten.     Zeits.  wiss.  Zool.,  bd.  24,  pp.  204-252,  i  taf. 
Packard,  A.  S.     1874.     On  the  Distribution  and  Primitive  Number  of  Spiracles  in  Insects. 

Amer.  Nat.,  vol.  8,  pp.  531-534- 
Palmen,  J.  A.     1877.     Zur   Morphologic  des  Tracheensystems.     10  +  i49   PP-.   2   taf. 

Helsingfors. 
Sharp,  D.     1877.     Observations  on  the  Respiratory  Action  of  the  Carnivorous  Water 

Beetles  (Dytiscidae).     Journ.  Linn.  Soc.  Zool.,  vol.  13,  pp.  161-183. 
Poletajew,  O.     1880.     Quelques  mots  sur  les  organes  respiratoires  des  larves  des  Odonates. 

Hora;  Soc.  Ent.  Ross.,  t.  15,  pp.  436-452,  2  pis. 
Krancher,  O.     1881.     Der  Bau  der  Stigmen  bei  den  Insekten.     Zeits.  wiss.  Zool.,  bd.  35, 

PP-  505-574,  taf.  28,  29. 
Vayssiere,  A.     1882.     Recherches  sur  I'organisation  des  larves  des  Ephemerines.     Ann.  Sc. 

nat.  Zool.,  ser.  6,  t.  13,  pp.  1-137,  pls.  i-n. 
Macloskie,  G.     1884.     The  Structure  of  the  Tracheae  of  Insects.     Amer.  Nat.,  vol.  18,  pp. 

567-573,  figs.  1-4. 
Plateau,   F.     1884.     Recherches   experimentales   sur   les   mouvements   respiratoires   des 

Insectes.     Mem.  Acad.  roy.  Belgique,  t.  45,  219  pp.,  7  pis.,  56  figs. 
Raschke,  E.  W.     1887.     Die  Larve  von  Culex  nemorosus.     Archiv  Naturg.,  jhg.  53,  bd.  i, 

pp.  133-163,  taf.  5,  6. 
Schmidt-Schwedt,  E.     1887.     Ueber  Athmung  der  Larven  und  Puppen  von  Donacia 

crassipes.     Berlin,  ent.  Zeits.,  ,bd.  31,  pp.  325-334,  taf.  5b. 
Haase,  E.     1889.     Die  Abdominalanhange  der  Insekten  mit  Beriicksichtigung  der  Myri- 

opoden.     Morph.  Jahrb.,  bd.  15,  pp.  331-435,  taf.  14,  15. 
Cajal,  S.  R.     1890.     Coloration  par  la  methode  de  Golgi  des  terminaisons  des  trachees  et 

des  nerfs  dans  les  muscles  des  ailes  des  insectes.    Zeits.  wiss.  Mikr.,  bd.  7,  pp.  332- 

342,  taf.  2,  figs.  1-3. 
Von  Wistinghausen,  C.     1890.     Ueber  Tracheenendigungen  in  den  Sericterien  der  Raupen . 

Zeits.  wiss.  Zool.,  bd.  49,  pp.  565-582,  taf.  27.* 
Stokes,  A.  C.     1893.     The  Structure  of  Insect  Tracheae,  with  Special  Reference  to  those  of 

Zaitha  fluminea.     Science,  vol.  21,  pp.  44-46,  figs.  1-7. 
29 


450  ENTOMOLOGY 

Miall,  L.  C.     1895,  1903.     The  Natural  History  of  Aquatic  Insects,     ii  +  39S  pp.,  116 

figs.    London  and  New  York.     Macmillan  &  Co. 
Sadones,  J.     1895.     L'appareil  digestif  et  respiratoire  larvaire  des  Odonates.     La  Cellule, 

t.  II,  pp.  271-325,  pis.  1-3. 
Gilson,  G.,  and  Sadones,  J.     1896.     The  Larval  Gills  of  the  Odonata.     Journ.  Linn.  Soc. 

Zool,  vol.  25,  pp.  413-418,  figs.  1-3. 
Holmgren,   E.     1896.     Ueber   das   respiratorische   Epithel   der   Tracheen   bei   Raupen. 

Festsk.  Lilljeborg,  Upsala,  pp.  79-96,  taf.  5,  6. 
Manunen,  H.     1912.     Ueber  die  Morphologie  der  Heteropteren  und  Homopterenstigmen. 

Zool.  Jahrb.,  Abt.  Anat.  Ont.,  bd.  34,  pp.  1 21-178,  taf.  7-9,  22  figs.* 
Deegener,  P.     1913.     Respirationsorgane.     In  Schroder:  Handbuch  der  Entomologie, 

bd.  I,  pp.  316-382,  figs.  212-274.* 
Vinal,  S.  C.     1919.     The  respiratory  system  of  the  Carolina  locust  (Dissosteira  Carolina 

Linne).     Journ.  N.  Y.  Ent.  Soc,  vol.  27,  pp.  19-32,  pis.  3-5. 

REPRODUCTIVE  SYSTEM 

Huxley,    T.    H.     1858-59.     On   the   Agamic   Reproduction   and  Morphology  of  Aphis 

Trans.  Linn.  Soc.  Zool.,  vol.  22,  pp.  193-236,  5  pis. 
Wagner,  N.     1865.     Ueber  die  viviparen  Gallmiickenlarven.     Zeits.  wiss.  Zool.,  bd.  15, 

■    pp.  106-117. 
Biitschli,  O.     1871.     Nahere  Mittheilungen  iiber  die  Entwicklung  und  den  Bau  der  Samen- 

faden  der  Insecten.     Zeits.  wiss.  Zool.,  bd.  21,  pp.  526-534,  taf.  40,  41. 
Will,  L.     1883.     Zur  Bildung  des  Eies  und  des  Blastoderms  bei  den  viviparen  Aphiden. 

Arbeit,  zool.-zoot.  Inst.  Univ.  Wiirzburg,  bd.  6,  pp.  217-258,  taf.  16. 
Palmen,  J.  A.     1884.    Ueber  paarige  Ausfiihrungsgange  der  Geschlechtsorgane  bei  Insecten. 

Ein  morphologische  Untersuchung.     108  pp.,  5  taf.     Helsingfors. 
Gilson,  G.     1885.     Etude  comparee  de  la  spermatogenese  chez  les  Arthropodes.    La 

Cellule,  t.  I,  pp.  7-188,  pis.  1-8.* 
Schneider,   A.     1885.     Die    Entwicklung   der    Geschlechtsorgane   der   Insecten.     Zool. 

Beitr.  von  A.  Schneider,  bd.  i,  pp.  257-300,  4  taf.     Breslau. 
Spichardt,  C.     1886.     Beitrag  zur  Entwickelung  der  mannlichen  Genitalien  und  ihrer 

Ausfiihrgange  bei  Lepidopteren.     Verb,  naturh.  Ver  Bonn,  jhg.  43,  pp.  1-34,  taf.  i. 
La  Valette  St.  George.     1886,  1887.     Spermatologische  Beitrage.     Arch.  mikr.  Anat., 

bd.  27,  pp.  1-12,  taf.  I,  2;  bd.  28,  pp.  1-13,  taf.  1-4;  bd.  30,  pp.  426-434,  taf.  25. 
Von  Wielowiejski,  H.  R.     1886.     Zur  Morphologie  des  Insectenovariums.     Zool.  Anz., 

jhg.  9,  pp.  132-139- 
Korschelt,  E.     1887.     Ueber  einige  interessante  Vorgange  bei  der  Bildung  der  Insekteneier. 

Zeits.  wiss.  Zool.,  bd.  45,  pp.  327-397,  taf.  18,  19. 
Oudemans,  J.  T.     1888.     Beitrage  zur  Kenntniss  der  Thysanura  und  Collembola.     Bijdr. 

Dierk.,  pp.  147-226,  taf.  1-3.     Amsterdam. 
Leydig,  F.     1889.     Beitrage  zur  Kenntniss  des  thierischen  Eies  im  unbefruchteten  Zu- 

stande.     Zool.  Jahrb.,  Abth.  Anat.  Ont.,  bd.  3,  pp.  287-432,  taf.  11-17. 
Lowne,  B.  T.     1889.     On  the  Structure  and  Development  of  the  Ovaries  and  their  Append- 
ages in  the  Blowfly  (Calliphora  erythrocephala).     Journ.  Linn.  Soc.  Zool.,  vol.  20, 

pp.  418-442,  pi.  28.* 
Ballowitz,  E.     1890.     Untersuchungen  iiber  die  Struktur  der  Spermatozoen,  zugleich  ein 

Beitrag  zur  Lehre  vom  feineren  Bau  der  kontraktilen  Elemente.     Die  Spermato- 
zoen der  Insekten.     (I.  Coleopteren.)     Zeits.  wiss.  Zool.,  bd.  50,  pp.  317-407, 

taf.  12-15. 
Henking,  H.     1890-92.     Untersuchungen  iiber  die  ersten  EntwicklungsvorgSnge  in  der 

Eiern  der  Insekten.    Zeits.  wiss.  Zool.,  bd.  49,  pp.  503-564,  taf.  24-26;  bd.  51,  pp 

685-736,  taf.  35-37;  bd.  54,  pp.  1-274,  taf.  1-12,  figs.  1-12. 


LITERATURE  45 1 

Heymons,  R.     1891.     Die  Entwicklung  der   weiblichen   Geschlechtsorgane  von  Phyllo- 

dromia  (Blatta)  germanica  L.    Zeits.  wiss.  Zool.,  bd.  53,  pp.  434-536,  taf.  18-20. 
Ingenitzky,  J.     1893.     Zur  Kenntnis  der  Begattungsorgane  derLibelluliden.     Zool.  Anz., 

jhg.  16,  pp.     405-407,  2  figs. 
Escherich,  K.     1894.     Anatomische  Studien  uber  das  mannliche  Genital-system  der  Cole- 

opteren.     Zeits.  wiss.  Zool.,  bd.  57,  pp.  620-641,  taf.  26,  figs.  1-3. 
Toyama,  K.     1894.     On  the  Spermatogenesis  of  the  Silk  Worm.     Bull.  Coll.  Agr.  Univ. 

Tokyo,  vol.  2,  pp.  125-157,  pis.  3,  4. 
Kluge,  M.H.  E.    1895.     Das  mannliche  Geschlechtsorgan  von  Vespa  germanica.     Archiv. 

Naturg.,  jhg.  61,  bd.  i,  pp.  159-198,  taf.  10. 
Peytoureau,  A.     1895.     Contributions  a  I'etude  de  la  morphologic  de  I'armure  genitale  des 

Insectes.     248  pp.,  22  pis.,  43  figs.     Paris. 
Wilcox,  E.  V.     1895.     Spermatogenesis  of  Caloptenus  femur-rubrum  and  Cicada  tibicen. 

Bull.  Mus.  Comp.  Zool.,  vol.  27,  pp.  1-32,  pis.  1-5.* 
Wilcox,  E.  V.     1896.     Futher  Studies  on  the  Spermatogenesis  of  Caloptenus  femur-rubrum . 

Bull.  Mus.  Comp.  Zool.,  vol.  29,  pp.  193-202,  pis.  1-3. 
Fenard,  A.     1897.     Recherches  sur  les  organes  complementaires  internes  de  I'appareil 

genital  des  Orthopteres.    Bull.  sc.  France  Belgique,  t.  29,  pp.  390-533,  pls-  24-28. 
Gross,  J.     1903.     Untersuchungeniiber  die  Histologic  des  Insectenovariums.    Zool.  Jahrb., 

Abth.  Anat.  Ont.,  bd.  18,  pp.  71-186,  taf.  6-14.* 
Griinberg,  K.     1903.     Unte|rsuchungen  liber  die  Keim-  und  Nahrzellen  in  den  Hoden  und 

Ovarien  der  Lepidoptera.     Zeits.  wiss.   Zool.,  bd.   74,  pp.  327-39S>  taf.  16-18. 
Holmgren,    N.     1903.     Ueber   vivipare    Insecten.     Zool.    Jahrb.,  bd.   19,  pp.  431-468, 

10  figs.* 
Felt,  E.  P.     1911.     Miastor  americana  Felt,  an  Account  of  Pedogenesis.     Twenty-sixth 

Rept.  St.  Ent.  N.Y.,  pp.  82-104,  figs.  7-9.* 
Deegener,  P.  1913,  1921.     Geschlechtsorgane.     In  Schroder:  Handbuch  der  Entomo- 

logie,  bd.  I,  pp.  466-533,  figs.  336-390-* 
Doncaster,  L.     1914.     The   Determination  of  Sex.     12  -}- 172  pp.,  22  pis.  Cambridge., 

Univ.  Press.     New  York,  G.  P.  Putnam's  Sons.* 
Doncaster,  L.     1920.     An    Introduction   to   the  Study  of   Cytology.  14  +  280  pp.,  figs. 

1-3 1,  pis.  1-24.     Cambridge.     Univ.  Press. 


EMBRYOLOGY 

Leuckart,  R.     1858.     Die  Fortpflanzung  und  Entwicklung  der  Pupiparen  nach  Beobach- 

tungen  an  Melophagus  ovinus.     Abh.  naturf.  Geseil.  HaUe,  bd.  4,  pp.  145-226,  3 

taf. 
Weismann,  A.     1863.     Die  Entwicklung  der  Dipteren  im  Ei,  nach  Beob'achtungen  an 

Chironomus  spec,  Musca  vomitoria  und  Pulex  canis.     Zeits.  wiss.  Zool.,  bd.  13, 

pp.  107-220,  7  taf.     Separate,  1864,  263  pp.,  14  taf. 
Metschnikoff,  E.     1866.     Embryologische  Studien  an  Insecten.     Zeits.  wiss.  Zool.,  bd.  16, 

pp.  389-500,  10  taf. 
Brandt,  A.     1869.     Beitrage  zur  Entwicklungsgeschichtc  der  Libelluliden  und  Hemipteren. 

Mem.  Acad.  St.  Petersbourg,  ser.  7,  t.  13,  pp.  1-33,  3  pis. 
Melnikow,N.     1869.     Beitrage  zur  Embryonalentwicklung  der  Insekten.    Archiv  Naturg., 

jhg.  35,  bd.  I,  pp.  136-189,  4  taf. 
Butschli,  O.     1870.     Zur  Entwicklutagsgeschichte  der  Bienc.     Zeits.  wiss.  Zool.,  bd.  20, 

pp.  519-564,  taf.  24-27. 
Kowalevsky,  A.     1871.     Embryologische  Studien  an  Wiirmern  und  Arthropoden.     Mem. 

Acad.  St.  Petersbourg,  ser.  7,  t.  16,  pp.  1-70,  12  pis. 


452  ENTOMOLOGY 

Hatschek,   B.     1877.     Beitrage   zur  Entwicklungsgeschichte  der  Lepidopteren.     Jenais. 

Zeits.  Naturw.,  bd.  ii,  38  pp.,  3  taf.,  2  figs. 
Bobretzky,  N.     1878.     Ueber  die  Bildung  des  Blastoderms  und  der  Keimblatter  bei  den' 

Insecten.   ,  Zeits.  wiss.  Zool.,  bd.  31,  pp.  195-215,  taf.  14. 
Will,  L.     1883.     Zur  Bildung  des  Eies  und  des  Blastoderms  bei  den  viviparen  Aphiden. 

Arbeit,  zool.-zoot.  Inst.  Univ.  Wiirzburg,  bd.  6,  pp.  217-258,  taf.  16. 
Ayers,  H.     1884.     On   the  Development   of  Qicanthus  niveus  and  its  Parasite  Teleas. 

Mem.  Best.  Soc.  Nat.  Hist.,  vol.  3,  pp.  225-281,  pis.  18-25,  figs.  1-41.* 
Patten,  W.     1884.     The  Development  of  Phryganids,  with  a  Preliminary  Note  on  the 

Development  of  Blatta  germanica.     Quart.  Journ.  Micr.  Sc,  vol.  24  (n.s.),  pp. 

549-602,  pis.  36a,  b,  c. 
Witlaczil,  E.     1884.     Entwicklungsgeschichte  der  Aphiden.     Zeits.  wiss.  Zool.,  bd.  40,  pp. 

559-696,  taf.  28-34.* 
Korotneflf,  A.     1886.     Die  Embryologie  der  Gryllotalpa.     Zeits.  wisB.  Zool,  bd.  41,  pp. 

570-604,  taf.  29-31. 
Blochmann,  F.     1887.     Ueber  die  Richtungskorper  bei  Insecteneiern.     Morph.  Jahrb., 

bd.  12,  pp.  544-574,  taf.  26,  27. 
Biitschli,  O.     1888.     Bemerkungen  iiber  die  Entwicklungsgeschichte  von  Musca.     Morph. 

Jahrb.,  bd.  14,  pp.  170-174,    3  figs. 
Graber,  V.     1888.     Ueber  die  Polypodie  bei  Insekten-Embryonen.     Morph.  Jahrb.,  bd. 

13,  pp.  586-615,  taf.  25,  26. 
.  Grabei,   V.     1888.     Ueber   die   primare    Segmentirung   des   Keimstreifs   der   Insekten. 

Morph..  Jahrb.,  bd.  14,  pp.  345-368,  taf.  14,  15,  4  figs. 
Henking,  H.    1888.    Die  ersten  Entwicklungsvorgange  im  Fliegenei  und  freie  Kernbildung. 

Zeits.  wiss.  Zool.,  bd.  46,  pp.  289-336,  taf.  23-26,  3  figs. 
"Will,   L.     1888.     Entwicklungsgeschichte   der  viviparen  Aphiden.     Zool.  Jahrb.,  Abth. 

Anat.  Ont.,  bd.  3,  pp.  201-286,  taf.  6-10. 
Cholodkovsky,    N.     1889.     Studien  zur    Entwicklungsgeschichte    der   Insekten.     Zeits. 

wiss.  Zool.,  bd.  48,  pp.  89-100.  taf.  8. 
Graber,  V.     1889.     Ueber  den  Bau  und  die  phylogenetische  Bedeutung  der  embryonalen 

Bauchanhange  der  Insekten.     Biol.  Centralb.,  jhg.  9,  pp.  355-363. 
Heider,  K.     1889.     Die  Embryonalentwicklung  von  Hydrophilus  piceus  L.     I.  Theil.     99 

pp.,  13  taf.,  9  figs.     Jena. 
Wheeler,  W.  M.     1889.     The  Embryology  of  Blatta  germanica  and  Doryphora  decem- 

lineata.     Journ.  Morph.,  vol.  3,  pp.  291-386,  pis.  15-21,  figs.  1-16. 
Carriere,  J.     1890.     Die  Entwicklung  der  Mauerbiene  (Chalicodoma  muraria   Fabr.)  im 

Ei.     Archiv  mikr.  Anat.,  bd.  35,  pp.  141-165,  taf.  8,  8a. 
Henking,  H.     1890-92.     Untersuchungen'  iiber  die  ersten  Entwicklungsvorgange  in  der 

Eiern  der  Insekten.    Zeits.  wiss.  Zool.,  bd.  49,  pp.  503-564,  taf.  24-26;  bd.   51,  pp. 

685-736,  taf.  35-37;  bd.  54,  pp.  1-274,  taf.  1-12,  figs.  1-12. 
Wheeler,  W.  M.     1890.     On  the  Appendages  of  the  First  Abdominal  Segment  of  Embryo 

Insects.     Trans.  Wis.  Acad.  Sc,  vol.  8,  pp.  87-140,  pis.  1-3.* 
Cholodkowsky,  N.     1891.     Die  Embryonalentwicklung,  von  Phyllodromia    (Blatta  ger- 
manica).    Mem.  Acad.  St.  Petersbourg,  ser.  7,  t.  38,  4  +  120  pp.,   6  pis.,  6  figs. 
Graber,  V.     1891.     Ueber  die  embryonale  Anlage  des  Blut-  und  Fettgewebes  der  Insekten; 

Biol.  Centralb.,  jhg.  11,  pp.  212-224. 
Wheeler,  W.  M.     1891.     Neuroblasts  in  the  Arthropod  Embryo.     Journ.  Morph.,  vol.  4, 

PP-  337-343,  I  fig- 
Graber,  V.     1892.     Ueber  die  morphologische  Bedeutung  der  ventralen    Abdominalan- 

hange  der  Insekten-Embryonen.     Morph.  Jahrb.,  bd.  17,  pp.  467-482,  figs.  1-6. 
Korschelt,   E.,   iind   Heider,  K.     1892.     Lehrbuch  der  vergleichenden  Entwicklungsge- 

shichte  der  wirbellosen  Thiere.     Heft  2,  pp.  761-890,  figs.  Jena.*  Trans.:  1899. 


LITERATURE  453 

M.  Bernard  and  M.  F.  Woodward.     Text-Book  of  the  Embryology  of  Inverte- 
brates.    12  +  441  pp.,  198  figs.     London,  Swan  Sonnenschein  &  Co.,  Ltd.;  New 

York,  The  Macmillan  Co.* 
Wheeler,  W.  M.     1893.     A  Contribution  to  Insect  Embryology.     Journ.   Morph.,  vol.  8, 

pp.  1-160,  pis.  1-6,  figs.  1-7. 
Heymons,  R.     1895.     Die  Embryonalentwickelung  von  Ucrmapteren  und  Orthopter^n 

unter  besonderer  Beriicksichtigung  der  Keimblatterbildung.     8  -|-  136  pp,  12  taf., 

33  figs.     Jena. 
He5rmons,  R.     1896.     Grundzuge  der  Entwickelung  und  des  Korperbaues  von  Odonaten 

und  Ephemeriden.     Anh.  Abh.  Akad.  Wiss.  Berlin,  66  pp.,  2  taf. 
Hesmions,  R.     1897.     Entwicklungsgeschichtliche  Untersuchungen  an  Lepisma  saccharina 

L.  Zeits.  wiss.  Zool.,  bd.  62,  pp.  583-631,  taf.  29,  30,  3  figs. 
Kulagin,  N.     1897.     Beitriige  zur  Kenntnis  der  Entwicklungsgeschichte  von  Platygaster, 

Zeits.  wiss.  Zool.,  bd.  63,  pp.  195-235,  taf.  10,  11. 
Claypole,  A.  M.     1898.     The  Embryology  and  Oogenesis  of  Anurida  maritima  (Guer.), 

Journ.  Morph.,  vol.  14,  pp.  219-300,  pis.  20-25,  11  figs. 
Uzel,  H.     1898.     Studien  uber  die  Entwicklung  der  apterygoten  Insecten.     6  +  58  pp 

6  taf.,  5  figs.     Berlin. 
Wilson,  E.  B.     1900.     The  Cell  in  Development  and  Inheritance.     21  +  483  pp.,  194  figs 

New  York  and  London.     The  Macmillan  Co. 
Marchal,  P.     1904.     La  Polyembryonie  Specifique.     Arch.  Zool.  exp.  gen.,  ser.  4,  t.  2,  pp 

257-335,  pis.  9-I3-* 
Heymons,  R.     1912.     Ueber  den  Genitalapparat  und  die  Entwicklung  von  Hemimerus 

talpoides  Walk.     Zool.  Jahrb.,  Supplement  15,  bd.  2,  pp.  141-184,  pis.  7-1 1,  3  figs 
Korschelt,    E.     1912.     Zur    Embryonalentwicklung    des  Dytiscus  marginalis  L.     Zool 

Jahrb.,  Supplement  15,  bd.2,  pp.  499-532,  24  figs.* 
Blunck,    H.     1914.     Die    Entwicklung   des    Dytiscus   marginalis   L.    vom    Ei    bis  zur 

Imago.  I  Teil.     Zeits.  wiss.  Zool.,  bd.  iii,  pp.  76-151,  figs.  1-31.* 
Nelson,  J.  A.      1915.     The  Embryology  of  the  Honey  Bee.      4  +  282  pp.,  95  figs.,  6  pis. 

Princeton,  N.  J.     Princeton  Univ.  Press.* 
Strindberg,   H.     1916.     Zur   Entwicklungsgeschichte   und  Anatomie   der    Mallophagen. 

Zeits.  wiss.  Zool.,  bd.  115,  pp.  382-459,  figs.  1-38.* 
Blunck,  H.     1917.     Die  Entwicklung  des  Dytiscus  marginalis  L.  vom  Ei  bis  zum  Imago. 

2  Teil.     Zeits.  wiss.  Zool.,  bd.  117,  pp.  1-129,  figs.  1-57.* 

POSTEMBRYONIC  DEVELOPMENT.      METAMORPHOSIS 

Weismann,  A.     1864.     Die  nachembryonale  Entwicklung  der  Musciden  nach  Beobach- 

tungen  an  Musca  vomitoria  und  Sarcophaga  carnaria.     Zeits.  wiss.  Zool.,  bd.  14, 

pp.  187-336. 
Weismann,  A.     1866.     Die  Metamorphose  von  Corethra  plumicornis.     Zeits.  wiss.  Zool., 

bd.  16,  pp.  45-127,  5  taf. 
Trouvelot,  L.     1867.     The  American  Silk  Worm.     Amer.  Nat.,  vol.  i,  pp.  30-38,  85-94, 

145-149,  4  figs.,  pis.  5,  6. 
Brauer,  F.     1869.     Betrachtungen  iiber  die  Verwandlung  der  Insekten  im  Sinne  der  Des- 

cendenz-Theorie.     Verh.  zool.-bot.   Gesell.  Wien,  bd.   19,  pp.   299-318;  bd.   28 

(1878),  1879,  pp.  151-166. 
Ganin,  M.     1869.     Beitrage  zur  Kenntniss  der  Entwickelungsgeschichte  bei  den  Insecten. 

Zeits.  wiss.  Zool.,  bd.  19,  pp.  381-451,  3  taf. 
Chapman,  T.  A.     1870.     On  the  Parasitisrn  of  Rhipiphorus  paradoxus.     Ann.  Mag.  Nat. 

Hist.,  ser.  4,  vol.  5,  pp.  191-198. 
Chapman,  T.  A.     1870.     Some  Facts  towards  a  Life  History  of  Rhipiphorus  paradoxus. 

Ann.  Mag.  Nat.  Hist.,  ser.  4,  vol.  6,  pp.  314-326,  pi.  16. 


454  ENTOMOLOGY 

Lubbock,  J.     1874,  1883.     On  the  Origin  and  Metamorphoses  of  Insects.     i6  +  io8  pp., 

6  pis.,  63  figs.     London.     Macmillan  &  Co. 
Ganin,  M.     1876.     [Materials  for  a  Knowledge  of  the  Postembryonal  Development  of 

Insects.     Warsaw.]     (In  Russian.)     Abstracts:  Amer.  Nat.,  vol.   11,  1877,  pp. 

423-430;  Zeits.  wiss.  Zool.,  bd.  28,  1877,  pp.  386-389. 
Riley,  C.  V.     1877.     On  the  Larval  Characters  and  Habits  of  the  Blister-beetles  belonging 

to  the  Genera  Macrobasis  Lee.  and  Epicauta  Fabr. ;  with  Remarks  on  other  Species 

of  the  Family  Meloidas.     Trans.  St.  Louis  Acad.  Sc,  vol.  3,  pp.  544-562,  figs.  35- 

39,  Pl-  5- 
Dewitz,  H.     1878.     Beitrage  zur  Kenntniss  der  postembryonalen  Gliedmassenbildung  bei 

den  Insecten.     Zeits.  wiss.  Zool.,  bd.  30,  suppl.,  pp.  78-105,  taf.  5. 
Packard,  A.  S.     1878.     Metamorphoses  [of  Locusts].     First  Rept.  U.  S.  Ent.  Comm.,  pp. 

279-284,  pis.  1-3,  figs.  19,  20. 
Metschnikoff,  E.     1883.     Untersuchungen  iiber  die  intracellulare  Verdauung  bei  wirbel- 

losen  Thieren.     Arb.  zool.  Inst.  Wien,  bd.  5,  pp.  141-168,  taf.  13,  14. 
Viallanes,  H.     1883.     Recherches  sur  I'histologie  des  Insectes  et  sur  les  phenomenes  histo- 

logiques  qui  accompagnent  le  developpement  post-embryonnaire  de  ces  animaux. 

Ann.  Sc.  nat.  Zool.,  ser.  6,  t.  14,  348  pp.,  18  pis. 
Kowalevsky,   A.     1885.     Beitrage   zur   nachembryonalen    Entwicklung   der   Musciden. 

Zool.  Anz.,  jhg.  8,  pp.  98-103,  123-128,  153-157. 
Schmidt,   O.     1885.     Metamorphose  und  Anatomie  des  mannlichen  Aspidiotus  nerii. 

Archiv  Naturg.,  jhg.  51,  bd.  i,  pp.  169-200,  taf.  9,  10. 
Witlaczil,  E.     1884.     Zur  Morphologie  und  Anatomie  der  Cocciden.     Zeits.  wiss.  Zool., 

bd.  43,  PP-  149-174,  taf.  5. 
Kowalevsky,  A.     1887.     Beitrage  zur  Kenntniss  der  nachembryonalen  Entwicklung  der 

Musciden.     Zeits.  wiss.  Zool.,  bd.  45,  pp.  542-594,  taf.  26-30. 
Van  Rees,  J.     1888.     Beitrage  zur  Kenntnis  der  inneren  Metamorphose  von  Musca  vomi- 

toria.     Zool.  Jahrb.,  Abth.  Anat.,Ont.,  bd.  3,  pp.  1-134,  taf.  i,  2,  14  figs. 
Hyatt,  A.,  and  Anns,  J.  M.     1890.     Insecta.     23  +  300  pp.,  13  pis.,  223  figs.     Boston. 

D.  C.  Heath  &  Co.* 
Bugnion,  E.     1891.     Recherches  sur  le  developpement  post-embryonnaire,  I'anatomie,  et 

les  mcEurs  de  I'Encyrtus  fuscicollis.     Rec.  zool.  Suisse,  t.  5,  pp.  435-534,  pis. 

20-25. 
Poulton,  E.  B.     1891.     The  External  Morphology  of  the  Lepidopterous  Pupa:  its  Relation 

to  that  of  the  other  Stages  and  to  the  Origin  and  History  of  Metamorphosis. 

Trans.  Linn.  Soc.  Zool.,  ser.  2,  vol.  5,  pp.  245-263,  pis.  26,  27. 
Korschelt,  E.,  iind  Heider,  K.     1892.     Lehrbuch  der  vergleichenden  Entwicklungsge- 

schichte  der  wirbellosen  Thiere.     Heft  2,  pp.  761-890,  figs.     Jena.* 
Miall,  L.  C,  and  Hammond,  A.  R.     1892.     The  Development  of  the  Head  of  Chironomus. 

Trans.  Linn.  Soc.  Zool.,  ser.  2,  vol.  5,  pp.  265-279,  pis.  28-31. 
Pratt,  H.  S.     1893.     Beitrage  zur  Kenntnis  der  Pupiparen.     Archiv  Naturg.,  jhg.  59,  bd. 

I,  pp.  151-200,  taf.  6. 
Gonin,  J.     1894.     Recherches  sur  la  metamorphose  des  Lepidopteres.     De  la  formation  des 

appendices  imaginaux  dans  la  cheniUe  du  Pieris  brassicae.     BuU.  Soc.  vaud.  Sc. 

nat.,  t.  30,  pp.  1-52,  5  pis. 
Miall,  L.  C.     1895.     The  Transformations  of  Insects.     Nature,  vol.  53,  pp.  153-158. 
Hyatt,  A.,  and  Anns,  J.  M.     1896.     The  Meaning  of  Metamorphosis.     Nat.  Sc,  vol.  8, 

pp.  395-403- 
Kulagin,  N.    1897  .    Beitrage  zur  Kenntnis  der  Entwicklungsgeschichte  von  Platygaster. 

Zeits.  wiss.  Zool.,  bd.  63,  pp.  195-235,  taf.  10,  11. 
Packard,  A.  S.     1897.     Notes  on  the  Transformations  of  Higher  Hymenoptera.     Journ. 

N.  Y.  Ent.  Soc,  vol.  4,  pp.  155-166,  figs.  1-5;  vol.  5,  pp.  77-87, 109-120,  figs.  6-13. 


LITERATURE  455 

Pratt,  H.  S.     1897.     Tmaginal  Discs  in  Insects.     Psyche,  vol.  8,  pp.  15-30,  ii  figs. 
Packard,  A,  S.     1898.     A  Text-Book  of  Entomology.     17  +  729  pp.,  654  figs.     New  York 

and  London.     The  Macmillan  Co.* 
Boas,  J.  E.  V.     1899.     Einige  Bemerkungen  iiber  die  Metamorphose  der  Insecten.     Zool. 

Jahrb.,  Abth.  Syst.,  bd.  12,  pp.  385-402,  taf.  20,  figs.  1-3. 
Lameere,  A.     1899.     La  raison  d'etre  des  metamorphoses  chez  les  Insectes.     Ann.  Soc. 

ent.  Belg.,  t.  43,  pp.  619-636. 
Perez,  C.     1899.     Sur  la  metamorphose  des  insectes.     Bull.  Soc.  ent.  France,  pp.  398-402. 
Wahl,  B.     1901.     Ueber  die  Entwicklung  der  hypodermalen  Imaginalscheiben  im  Thorax 
und  Abdomen  der  Larve  von  Eristalis  Latr.     Zeits.  wiss.  Zool.,  bd.  70,  pp.  171-191, 

taf.  9,  figs.  1-4.    . 
Perez,  C.     1902.     Contribution  a  I'etude  des  metamorphoses.     Bull.  sc.  France.  Belg.,  t. 

37,  pp.  195-427,  pis.  10-12,  32  figs. 
Deegener,  P.     1904,     Die  Entwicklung  des  Darmcanals  der  Insecten  wahrend  der  Meta- 
morphose.    Zool.  Jahrb.,  Abth.  Anat.  Ont.,  bd.  20,  pp.  499-676,  taf.  33-43-* 
Powell,  P.  B.     1904-05.     The  Development  of  Wings  of  Certain  Beetles,  and  some  Studies 

of  the  Origin  of  the  Wings  of  Insects.     Journ.  N.  Y.  Ent.  Soc,  vol.  12,  pp.  237-243, 

pis.  11-17;  vol.  13,  pp.  5-22.* 
Perez,  C.     1910.     Recherches  histologiques  sur  la  metamorphose  des  Muscides.     Arch. 

Zool.  exp.  gen.,  ser.  5,  t.  4,  pp.  1-270,  pis.  1-16,  162  figs. 
Carpenter,  G.  H.     1921.     Insect  Transformation.     10  +  282  pp.,  1 24  figs.,  4  pis.    London. 

Methuen  &  Co. 

AQUATIC    INSECTS 

Dufotir,  L.     1849.     Des  divers  modes  de  respiration  aquatique  dans  les  insectes.     Compt  * 

rend.  Acad.  Sc,  t.  29,  pp.  763-770.     Ann.  Mag.  Nat.  Hist.,  ser.  2,  vol.  6,  i85o,pp- 

112-118. 
Dufour,  L.     1852.     Etudes  anatomiques  et  physiologiques  et  observations  sur  les  larves 

des  Libellules.     Ann.  Sc.  nat.  Zool.,  ser.  3,  t.  17,  pp.  65-110,  3  pis. 
Hagen,  H.  A.     1853.     Leon  D  ufour  uber  die  Larven  der  Libellen  mit  Beriicksichtigung  der 

friiheren  Arbeiten.      (Ueber  Respiration  der  Insecten.)     Stett.  ent.  Zeit.,  bd.  14, 

pp.  98-106,  237-238,  260-270,  311-325,  334-346. 
Williams,  T.     1853-57.     On  the  Mechanism  of  Aquatic  Respiration  and  on  the  Structure 

of  the  Organs  of  Breathing  in  Invertebrate  Animals.     Ann.  Mag.  Nat.  Hist.,  ser. 

2,  vols.  12-19,  17  pis. 
Oustalet,  E.     1869.     Note  sur  la  respiration  chez  les  nymphes  des  Libellules.     Ann.  Sc. 

nat.  Zool.,  ser.  5,  t.  11,  pp.  370-386,  3  pis. 
Sharp,  D.     1877.     Observations  on  the  Respiratory  Action  of  the  Carnivorous  Water 

Beetles  (Dytiscidae).     Journ.  Linn.  Soc.  Zool.,  vol.  13,  pp.  161-183. 
Poletajew,  O.     1880.     Quelques  mots  sur  les  organes  respiratoires  des  larves  des  Odonates. 

Horse  Soc.  Ent.  Ross.,  t.  15,  pp.  436-452,  2  pis. 
Vayssiere,  A.     1882.     Recherches  sur  I'organisation  des  larves  des  Ephemerines.     Ann. 

Sc.  nat.  Zool.,  ser.  6,  t.  13,  pp.  1-137,  pis.  i-ii. 
Macloskie,  G.     1883.     Pneumatic  Functions  of  Insects.     Psyche,  vol.  3,  pp.  37S~378. 
White,  F.  B.     1883.     Report  on  the  Pelagic  Hemiptera.     Rept.  Sc.  Res.  Voy.  H.  M.  S. 

Challenger,  1873-1876,  Zoology,  vol.  7,  82  pp.,  3  pis. 
Comstock,  J.  H.     1887.     Note  on  Respiration  of  Aquatic  Bugs.     Amer.  Nat.,  vol.  21,  pp. 

577-578. 
Schwedt,  E.     1887.     Ueber    Athmung  der  Larven  und  Puppen  von  Donacia  crassipes. 

Berl.  ent.  Zeits.,  bd.  31,  pp.  325-334,  taf.  5b. 
Amans,  P.  C,     1888.      Comparaisons  des  organes  de  la  locomotion  aquatique.     Ann.  Sc. 

nat.  Zool.,  ser.   7,  t.  6,  pp.  1-164,  pis.  1-6. 


456  ENTOMOLOGY 

Garman,  H.     1889.     A  Preliminary  Report  on  the  Animals  of  the  Mississippi   Bottoms 
near  Quincy,  Illinois,  in  August  1888.     Bull.  111.  St.  Lab.  Nat.  Hist.,  voL  3,  pp. 

123-184. 
Miall,  L.  C.     1891.     Some  Difficulties  in  the  Life  of  Aquatic  Insects.      Nature,  vol.  44,  pp. 

457-462. 
Walker,  J.  J.     1893.     On  the  Genus  Halobates,  Esch.,  and  other  Marine  Hemiptera.     Ent. 

Mon.  Mag.,  ser.  2,  vol.  4  (29),  pp.  227-232. 
Carpenter,  G.  H.     1895.     Pelagic  Hemiptera.     Nat.  Sc,  vol.  7,  pp.  60-61. 
Hart,  C.  A.     1895.     On  the  Entomology  of  the  Illinois  River  and  Adjacent  Waters.     Bull. 

111.  St.  Lab.  Nat.  Hist.,  vol.  4,  PP-  149-273,  pls.  1-15- 
MiaU.L.  C.     1895,1903.     The  Natural  History  of  Aquatic  Insects.     11  +  395  pp.,  116  figs. 

London  and  New  York.     Macmillan  &  Co.* 
Sadones,  J.     1895.     L'appareil  digestif  et  respiratoire  larvaire  des  Odonates.     La  Cellule, 

t.  II,  pp.  271-325,  pis.  1-3. 
Gilson,  G.,  and  Sadones,  J.     1896.     The  Larval  Gills  of  the  Odonata.     Journ.  Linn.  Soc. 

Zool,  vol.  25,  pp.  413-418,  figs.  1-3. 
Comstock,  J.  H.     1897,  1901.     Insect  Life.     6  +  349  pp.,  18  pis.,  296  figs.     New  York. 

D.  Appleton  &  Co.* 
Needham,  J.  G.     1900.     Insect  Drift  on  the  Shore  of  Lake  Michigan.     Occas.  Mem. 

Chicago  Ent.  Soc,  vol.  i,  pp.  1-8,  i  fig. 
Needham,  J.  G.,  and  Betten,  C.     1901.     Aquatic  Insects  in  the  Adirondacks.     Bull. 

N.  Y.  St.  Mus  ,  no.  47,  PP-  383-612,  36  pis.,  42  figs. 
Needham,  J.  G.,  MacGillivray,  A.  D.,  Johamisen,  O.  A.,  and  Davis,  K.  C.     1903.    Aquatic 

Insects  in  New  York  State.    Bull.  N.  Y.  St.  Mus.,  no.  68,  321  pp.,  52  pis.,  26  figs.* 
Lutz,  F.  E.     1913.     Factors  in  Aquatic  Environments.     Jour.  N.  Y.  Ent.  Soc,  vol.  21, 

pp.  1-4. 
Sleight,  C.  E.     1913.     Relations  of  Trichoptera  to  their  Environment.     Jour.  N.  Y.  Ent. 

Soc,  vol.  21,  pp.  4-8,  pi.  I. 
Osbum,R.  C.     1913.     Odonata  in  Relation  to  the  Hydrophytic  Environment.     Jour.  N.  Y. 

Ent.  Soc,  vol.  21,  pp.  9-1 1. 
Barber,  H.  G.     1913.     Aquatic  Hemiptera.     Jour.  N.  Y.  Ent.  Soc,  voL  21,  pp.  29-32. 
Leng,  C.  W.     1913.     Aquatic  Coleoptera.     Jour.  N.  Y.  Ent.  Soc,  vol.  21,  pp.  32-42. 
Sherman,  J.  D.,  Jr.     1913.     Some  Habits  of  the  Dytiscidae.     Journ.  N.  Y.  Ent.  Soc,  vol. 

21,  pp.  43-54- 
Grossbeck,  J.  A.     1913.     The  Relation  of  Mosquitoes  to  their  Environment.     Jour. 

N.  Y.  Ent.  Soc,  vol.  21,  pp.  55-61. 
Needham,  J.  G.,  and  Lloyd,  J.  T.     1916.     The  Life  of  Inland  Waters.     438  pp.,  244  figs. 

Ithaca,  N.  Y.     Comstock  Pub.  Co.* 
Needham,  J.  G.     1918.     Aquatic  Insects.     In  Ward  and  Whipple:  Fresh- water  Biology, 

pp.  876-946,  figs.  1354-1392.     New  York.     John  Wiley  &  Sons,  Inc.* 
Welch,  P.    S.     1919.     The  Aquatic  Adaptations  of  Pyrausta  penitalis  Grt.  (Lepidoptera). 

Ann.  Ent.  Soc.  Amer.,  vol.  12,  pp.  213-226.* 
Muttkowski,  R.  A.     1920.     The  Respiration  of  Aquatic  Insects.     Bull.  Brooklyn  Ent. 

Soc,  vol.  IS,  pp.  89-96,  131-141.* 
Muttkowski,  R.  A.     1921.     Studies  on  the  Respiration  of  Insects.     Ann.  Ent.  Soc.  Amer., 

vol.  14,  pp.  150-156.* 


COLOR  AND  COLORATION 

Higgins,  H.  H.     1868.     On  the  Colour-Patterns  of  Butterflies.     Quart.  Journ.  Sc,  vol. 
pp.  323-329,  1  Pl- 


LITERATURE  457 

Weismanp,  A.     1875.     Studien  zur  Descendenztheorie.     I.   Ueber  den  Saison  Dimor- 

phismus  der  Schmetterlinge.     Leipzig.     Trans. :  i8vSo-8i.     R.  Meldola.    Studies 
in  the  Theory  of  Descent.     554  pp.,  8  pis.     London. 
Scudder,  S.  H,     1877.     Antigeny,  or  Sexual  Dimorphism  in  Butterflies.     Proc.  Amer. 

Acad.  Arts  Sc,  vol.  12,  pp.  150-158. 
Dorfmeister,  G.     1880.     Ueber    den    Einfluss  der    Temperatur  bei  der  Erzeugung  der 

Schmctterlingsvarietaten.     Mitth.  naturw.  Ver.  Steiermark,  jhg.  1879,  pp.  3-8, 
I  taf. 
Scudder,   S.  H.     1881.     Butterflies;  their  Structure,  Changes  and  Life-Histories,   with 

Special   Reference  to  American  Forms.     9  +  322   pp.,    201    figs.     New   York. 

Henry  Holt  &  Co. 
Hagen,  H.  A.     1882.     On  the  Color  and  the  Pattern  of  Insects.     Proc.  Amer.  Acad.  Arts 

Sc,  vol.  17,  pp.  234-267. 
Dimmock,  G.     1883.     The  Scales  of  Coleoptera.     Psyche,  vol.  4,  pp.  3-1 1,  23-27,  43-47, 

63-71,  II  figs.* 
Poulton,  E.  B.     1884.     Notes  upon,  or  suggested  by  the  Colours,  Markings  and  Protective 

Attitudes  of  certain  Lepidopterous  Larvae  and  Pupae,  and  of  a  phytophagous 

hymenopterous  larva.     Trans.  Ent.  Soc.  London,  pp.  27-60,  pi.  i. 
Poulton,  E.  B.     1885.     The  Essential  Nature  of  the  Colouring  of  Phytophagous  Larvae  and 

their  Pupae,  etc.     Proc.    Roy.   Soc.  London,  vol.  38,  pp.  269-315 
Poulton,  E.  B.     1885.     Further  Notes  upon  the  Markings  and  Attitudes  of  Lepidopterous 

Larvae.     Trans.  Ent.  Soc.  London,  pp.  281-329,  pi.  7. 
Poulton,  E.  B.     1887.     An  Enquiry  into  the  Cause  and  Extent  of  a  Special  Colour-Relation 

between  Certain  Exposed  Pupae  and  the  Surfaces    which  immediately  surround 

them.     Phil.  Trans.  Roy.  Soc.  London,  vol.  178,  pp.  311-441,  pi.  26. 
Dixey,  F.  A.     1890.     On  the  Phylogenetic  Significance  of  the  Wing-Markings  in  certain 

Genera  of  the  Nymphalidae.     Trans.  Ent.  Soc.  London,  pp.  89-129,  pis.   1-3. 
Merrifield,  F.     1890.     Systematic  temperature  experiments  on  some  Lepidoptera  in  all 

their  stages.     Trans.  Ent.  Soc.  London,  pp.  131-159,  pis.  4,  5. 
Poulton,  E.  B.     1890.     The  Colours  of  Animals.     13  +  360  pp.,  i  pi.,  66  figs.     New  York. 

D.  Appleton  &  Co. 
Seitz,  A.     1890,  1893.     Allgemeine  Biologie  der  Schmetterlinge.     Zool.  Jahrb.,  Abth.  Syst., 

etc.,  bd.  5,  pp.  281-343;  bd.  7,  pp.  131-186.* 
Coste,  F.  H.  P.     1890-91.     Contributions  to  the  Chemistry  of  Insect  Colors.     Entomol- 
ogist, vol.  23,  pp.  128-132,  etc.;  vol.  24,  pp.  9-15,  etc. 
Merrifield,  F.     1891.     Conspicuous  effects  on  the  markings  and  colouring  of  Lepidoptera 

caused  by  exposure  of  the  pupae  to  different  temperature  conditions.     Trans.  Ent. 

Soc.  London,  pp.  155-168,  pi.  9. 
Urech,  F.     1891.     Beobachtungen  iiber  dieverschiedenen  Schuppenfarbenunddiezeitliche 

Succession   ihres  Auftretens   (Farbenfelderung)   auf  den  Puppenfliigelchen  von 

Vanessa  urticae  und  lo.     Zool.  Anz.,  jhg.  14,  pp.  466-473. 
Beddard,  F.  E.     1892.     Animal  Coloration.     8 -f  288  pp.,  4  pis.,  36  figs.    London,  Swan, 

Sonnenschein  &  Co.     New  York,  Macmillan  &  Co. 
Gould,  L.  J.     1892.     Experiments  in  1890  and  1891  on  the  colour-relation  between  certain 

lepidopterous  larvae  and  their  surroundings,  together  with  some  other  observations 

on  lepidopterous  larvae.     Trans.  Ent.  Soc.  London,  pp.  215-246,  pi.  11. 
Merrifield,  F.     1892.     The  effects  of  artificial  temperature  on  the  colouring  of  several 

species  of  Lepidoptera,  with  an  account  of  some  experiments  on  the  effects  of  light. 

Trans.  Ent.  Soc.  London,  pp.  33-44. 
Poulton,  E.  B.     1892.     Further  experiments  upon   the  colour-relation   between  certain 

lepidopterous  larvae,  pupae,  cocoons  and  imagines  and  their  surroundings.     Trans. 

Ent.  Soc.  London,  pp.  293-487,  pis.  14,  15. 


458  ENTOMOLOGY 

Urech,  F.     1892.       Bebachtungen  uber  die  zeitlicbe  Succession  der  Auf  tretens  der  Farben- 

felder  auf  den  Puppenflugelchen  von  Pieris  brassicae.     Zool.  Anz.,  jhg.  15,  pp. 

284-290,  293-299. 
Weismann,  A.     1892,  1898,     The  Germ-Plasm.     Trans,  by  W.  N.  Parker  and  H.  Ronn- 

feldt.     See  pp.  399-409,  on  climatic  variation  in  butterflies. 
Dixey,  F.  A.     1893.     On  the  phylogenetic  significance  of  the  variations  produced  by  differ- 
ence of  temperature  in  Vanessa  atalanta.     Trans.  Ent.  Soc.  London,  pp.  69-73. 
Merrifield,  F.     1893.     The  effects  of  temperature  in  the  pupal  stage  on  the  colouring  of 

Pieris   napi,   Vanessa   atalanta,    Chrysophanus  phloeas,  and  Ephyra  punctaria. 

Trans.  Ent.  Soc.  London,  pp.  55-67,  pi.  4. 
Poulton,  E.  B.     1893.     The  Experimental  Proof  that  the  Colours  of  certain  Lepidopterous 

Larvae  are  largely  due  to  modified  plant  Pigments  derived  from  Food.     Proc.  Roy. 

Soc.  London,  vol.  54,  pp.  417-430,  pis.  3,  4. 
Urech,  F.     1893.     Beitrage  zur  Kenntniss  der  Farbe  von  Insektenschuppen.     Zeits.  wiss. 

Zool.,  bd.  57,  pp.  306-384. 
Bateson,  W.     1894.     Materials  for  the  Study  of  Variation  treated  with  especial  Regard  to 

Discontinuity  in  the  Origin  of  Species.     16  +  598  pp.,  209  figs.     London  and  New 

York.     Macmillan  &  Co. 
Dixey,  F.  A.     1894.     Mr.  Merrifield's  Experimen  ts  in  Temperature- Variation  as  bearing  on 

Theories  of  Heredity.     Trans.  Ent.  Soc.  London,  pp.  439-446. 
Kellogg,  V.  L.     1894.     The  Taxonomic  Value  of  the  Scales  of  the  Lepidoptera.     Kansas 

Univ.  Quart.,  vol.  3,  pp.  55-89,  pis.  9,  10,  figs.  1-17. 
Merrifield,  F.     1894.     Temperature  Experiments  in  1893  on  several  species  of  Vanessa 

and  other  Lepidoptera.     Trans.  Ent.  Soc.  London,  pp.  425-438,  pi.  9. 
Hopkins,  F.  G.     1895.     The  Pigments  of  the  Pieridae:  A  Contribution  to  the  Study  of 

Excretory    Substances    which  function  in  Ornament.     Phil.    Trans.  Roy.   Soc. 

London,  vol.  186,  pp.  661-682. 
Spuler,  A.     1895.     Beitrag  zur  Kenntniss  des  feineren  Baues  und  der  Phylogenie  der 

Fliigelbedeckung  der  Schmetterlinge.     Zool.  Jahrb.,  Abth.  Anat.  Ont.,  bd.  8,  pp. 

520-543,  taf.  36. 
Standfuss,  M.     1895.     On  the  Causes  of  Variation  and  Aberration  in  the  Imago  Stage  of 

Butterflies,  with  Suggestions  on  the  Establishment  of  New  Species.     Trans,  by 

F.  A.  Dixey.     Entomologist,  vol.  28,  pp.  69-76,  102-114,  142-150. 
Mayer,  A.  G.    1896.    The  Development  of  the  Wing  Scales  and  their  Pigment  in  Butterflies 

and  Moths.     Bull.  Mus.  Comp.  Zool.,  vol.  29,  pp.  209-236,  pis.  1-7. 
Weismann,  A.     1896.     New  Experiments  on  the  Seasonal  Dimorphism  of  Lepidoptera. 

Trans,  by  W.  E.  Nicholson.     The  Entomologist,  vol.  29,  pp.  29-39,  etc. 
Brunner  von  Wattenwyl,  C.     1897.     Betrachtungen  iiber  die  Farbenpracht  der  Insekten. 

16  pp.,  9  taf.     Leipzig.     Trans,  by  E.  J.  Bles:  Observations  on  the  Coloration  of 

Insects.     16  pp.,  9  pis.    Leipsic. 
Fischer,  E.     1897-99.     Beitrage   zur   experimentellen  Lepidopterologie.     lUustr.     Zeits. 

Ent.,  bd.  2-4,  12  taf. 
Mayer,  A.  G.     1897.     On  the  Color  and  Color-Patterns  of  Moths  and  Butterflies.     Proc. 

Bost.  Soc.  Nat.  Hist.,  vol.  27,  pp.  243-330,  pis.  i-io.     Also  Bull.  Mus.  Comp. 

Zool.,  vol.  30,  pp.  169-256,  pis.  i-io. 
Von  Linden,  Grafin,  M.     1898.     Untersuchungen  iiber  die  Entwicklung  der  Zeichnung  des 

Schmetterlingsfliigels  in  der  Puppe.     Zeits.  wiss.  Zool.,  bd.  65,  pp.  1-49,  taf.  1-3. 
Newbigin,  M.  I.     1898.     Colour  in  Nature.     12 -f  344  pp.     London.     John  Murray.* 
Von  Linden,  Grafin,  M.     1899.     Untersuchungen  iiber  die  Entwickelung  der  Zeichnung 

der  Schmetterlingsfliigels  in  der  Puppe.     lUustr.  Zeits.  Ent.,  bd.  4,  pp.  19-22. 
Von  Linden,  la  Comtesse  M.     1902.    Le  dessin  des  ailes  des  Lepidopteres.     Recherches 


LITERATURE  459 

sur  son  evolution  dans  I'ontogenese  et  la  phylogenese  des  especes,  son  origine  et  sa 

valeur  systematique.     Ann.  Sc.  nat.  Zool.,  ser.  8,  t.  14,  pp.  1-196,  pis.  1-20. 
Weismann,  A.     1902.    Vortrage  iiber  Descendenztheorie.     2  vols.     12  +  456  pp.,  95  figs.; 

6  +  462  pp.,  3  pis.,  36  figs.     Jena.     G.  Fischer.     See  pp.  65-102. 
Von  Linden,  Grafin  M.     1903.     Morphologische  und  physiologisch-chemische  Untersuch- 

ungen  iiber  die  Pigmente  der  Lepidopteren.     i.  Die  gelben  und  roten  Fafbstoffe 

der  Vanessen.     Archiv  ges.  Phys.,  bd.  98,  pp.  1-89,  i  taf.,  3  figs. 
Poulton,  E.  B.     1903.     Experiments  in   1893,   1894  and   1896  upon  the  colour-relation 

between  lepidopterous  larvae  and  their  surroundings,  and  especially  the  effect  of 

lichen-covered    bark   upon  Odontopera  bidentata,  Gastropacha  quercifolia,  etc. 

Trans.  Ent.  Soc.  London,  pp.  311-374,  pis.  16-18. 
Tower,  W.  L.     1903.     The  Development  of  the  Colors  and  Color  Patterns  of  Coleoptera, 

with  Observations  upon  the  Development  of  Color  in  other  Orders  of  Insects. 

Univ.  Chicago  Decenn.  Publ.,  vol.  10,  pp.  1-40,  pis.  1-3. 
Vernon,  H.  M.     1903.     Variation  in  Animals  and  Plants.     9+415  pp-     New  York. 

Henry  Holt  &  Co. 
Enteman,  W.  M.     1904.     Coloration  in  Polistes.     Publ.  No.,  19  Carnegie  Inst.  Washington, 

88  pp.,  6  pis.,  26  figs.* 
Von   Linden,  Grafin   M.     1906.     Physiologische   Untersuchungen    an   Schmetterlingen. 

Zeits.  wiss.  Zool,  bd.  82,  pp.  411-444,  taf.  25.* 
Tower,  W.  L.     1906.     An  Investigation  of  Evolution  in  Chrysomelid  Beetles  of  the  Genus 

Leptinotarsa.     10  +  320  pp.,  31  figs.,  30  pis.     Washington,  D.  C.   Carnegie  Inst. 
Friese,  H.,  and  v.  Wagner,  F.     1910.     Zoologischen  Studien  an  Hummeln.      Zool.  Jahrb., 

Abt.  Syst.  Geogr.  Biol.,  bd.  29,  pp.  1-104,  taf.  1-7,  20  figs.* 
Johnson,  R.  H.     1910.     Determinate  Evolution  in  the  Color  Pattern  of  the  Lady  Beetles. 

Publ.  No.  122,  Carnegie  Inst.  Wash.,  104  pp.,  92  figs. 
Gerould,  J.  H.     1911.     The  Inheritance  of  Polymorphism  and  Sex  in  Colias  philodice. 

Amer.  Nat.,  vol.  45,  pp.  257-283,  figs.  1-5.* 
Gortner,  R.  A.     1911.     Studies  on  Melanin.     Amer.  Nat.,  vol.  45,  pp.  743-75S-* 
Michelson,  A.  A.     1911.     On  Metallic  Colouring  in  Birds  and  Insects.     Phil.  Mag.,  ser.  6, 

vol.  21,  pp.  554-567.  pl-  4- 
Von  Voss,  H.     1911.     Die  Entwicklung  der   Raupenzeichnung  b?i  einigen  Sphingiden. 

Zool.  Jahrb.,  Abt.  Syst.  Geogr.  Biol,  bd.  30,  pp.  573-642,  taf.  16-19,  6  figs.* 
Friese,  H.,  and  v.  Wagner,  F.     1912.     Zoologische  Studien  an  Hummeln.     Zool.  Jahrb., 

Supplement  15,  bd.  i,  pp.  155-210,  taf.  5-9,  20  figs. 
Gerould,  J.  H,     1916.     The  Inheritance  of  Seasonal  Polymorphism  in  Butterflies.     Amer. 

Nat.,  vol.  50,  pp.  310-316. 
Shelford,  V.  E.     1917.     Color  and  Color-pattern  Mechanism  of  Tiger  Beetles.     111.  Biol. 

Monogr.,  vol.  3,  no.  4,  134  pp.,  32  pis.* 
Gerould,  J.  H.     1921.     Blue-green  caterpillars;  the  origin  and  ecology  of  a  mutation  in 

haemolymph  color  in  Colias  (Eurymus)  philodice.     Journ.  Exp.  Zool.,   vol.   34, 

pp.  385-416,  I  fig.,  I  pl.* 

ADAPTIVE    COLORATION 

Bates,  H.  W.     1862.     Contributions  to  an  Insect  Fauna  of  the  Amazon  Valley.     Lepidop- 

tera:  Heliconidae.     Trans.  Linn.  Soc.  Zool.,  vol.  23,  pp.  495-566,  pis.  55,  56. 
Wallace,  A.  R.     1867.     [Theory  of  Warning  Coloration.]     Trans.  Ent.  Soc.  London,  ser.  3, 

vol.  5,  Proc,  pp.  80-81. 
Butler,  A.  G.     1869.     Remarks  upon  certain  Caterpillars.,  etc.,  which  are  unpalatable  to 

their  enemies.     Trans.  Ent.  Soc.  London,  pp.  27-29. 
Trimen,  R.     1869.     On  some  remarkable  Mimetic  Analogies  among  African  Butterflies. 

Trans.  Linn.  Soc.  Zool.,  vol.  26,  pp.  497-522,  pis.  42,  43. 


460  ENTOMOLOGY 

Meldola,  R.     1873.     On  a  certain  Class  of  Cases  of  Variable  Protective  Colouring  in  Insects. 

Proc.  Zool.  Soc.  London,  pp.  153 — 162. 
Miiller,  F.     1879.     Ituna  and  Thyridia;  a  remarkable  case  of  Mimicry  in  Butterflies. 

Trans.,  R.  Meldola,  Proc.  Ent.  Soc.  London,  pp.  20-29,  ^S^.  1-4. 
Blackiston,  T.,  and  Alexander,  T.     1884.     Protection  by  Mimicry — A  Problem  in  Mathe- 
matical Zoology.     Nature,  vol.  29,  pp.  405-406. 
Poulton,  E.  B.     1884.     Notes  upon  or  suggested  by  the  Colours,  Markings  and  Protective 

Attitudes  of  certain  Lepidopterous  Larvae  and  Pupae,  and  of  a  phytophagous 

hymenopterous  larva.     Trans.  Ent.  Soc.  London,  pp.  27-60,  pi.  i. 
Poulton,  E.  B.     1885.     Further  notes  upon  the  markings  and  attitudes  of  lepidopterous 

larvae.     Trans.  Ent.  Soc.  London,  pp.  281-329,  pi.  7. 
Poulton,  E.  B.     1887.     The  Experimental  Proof  of  the  Protective  Value  of  Colour  and 

Markings  in  Insects  in  reference  to  their  Vertebrate  Enemies.     Proc.  Zool.  Soc. 

London,  pp.  191-274. 
Wallace,   A.   R.     1889.     Darwinism.     16  +  494   pp.,  37  figs.     London  and  New  York. 

Macmillan  &  Co. 
Poulton,  E.B.     1890.     The  Colours  of  Animals.     13  +  360  pp.,  i  pi.,  66  figs.     New  York. 

D.  Appleton  &  Co. 
Beddard,  F.  E.     1892.     Animal  Coloration.     8  +  288  pp.,  4  pis.,  36  figs.     London,  Swan, 

Sonnenschein  &  Co.     New  York,  MacmiUan  &  Co. 
Haase,  E.     1893.     Untersuchungen  iiber  die  Mimicry  auf  Grundlage  eines  natiirlichen 

Systems  der  Papilioniden.     Bibl.  Zool. ,  Heft  8,  Theil  i ,  1 20  pp. ,  6  taf . ;  Theil  2,161 

pp.,  8  taf.     Trans.  Theil  2,  C.  M.  ChUd,  Stuttgart,  1896,  154  pp.,  8  pis. 
Finn,  F.     1895-97.     Contributions  to  the  Theory  of  Warning    Colours    and    Mimicry. 

Journ.  Asiat.  Soc.  Bengal,  vols.  64-67. 
Dixey,  F.  A.     1896.     On  the  Relation  of  Mimetic  Patterns  to  the  Original  Form.     Trans. 

Ent.  Soc.  London,  pp.  65-79,  pis.  3-5. 
Piepers,  M.  C.     1896.     Mimetisme.     Cong.  Intern.  Zool.,  3  Sess.,  Leyden,  pp.  460-476. 
Dixey,  F.  A.     1897.     Mimetic  Attraction.     Trans.  Ent.  Soc.  London,  pp.  317-331,  pi.  7. 
Mayer,  A.  G.      1897.      On  the  Color  and  Color-Patterns  of  Moths  and  Butterflies.     Proc. 

Bost.  Soc.  Nat.  Hist.,  vol.  27,  pp.  243-330,  pis.  i-io.     Also  Bull.  Mus.  Comp. 

Zool.,  vol.  30,  pp.  169-256,  pis.  i-ic* 
Trimen,  R.     1897.     Mimicry  in  Insects.     Proc.  Ent.  Soc.  London,  pp.  74-97.* 
Webster,  F.  M.     1897.     Warning  Colors,  Protective  Mimicry  and  Protective  Coloration. 

27th  Ann.  Rept.  Ent.  Soc.  Ontario  (1896),  pp.  80-86,  figs.  80-82.  • 
Newbigin,  M.  I.     1898.     Colour  in  Nature.     12  +  344  pp.     London.     John  Murray.* 
Poulton,  E.  B.     1898.     Natural  Selection  the  Cause  of  Mimetic  Resemblance  and  Common 

Warning  Colors.     Journ.  Linn.  Soc.  Zool.,  vol.  26,  pp.  558-612,  pis.  40-44,  figs.  1-7. 
Judd,  S.  D.     1899.     The  Efficiency  of  Some  Protective  Adaptations  in  Securing  Insects 

from  Birds.     Amer.  Nat.,  vol.  33,  pp.  461-484. 
Marshall,  G.  A.  K.,  and  Poulton,  E.  B.     1902.     Five  Years'  Observations  and  E.xperi- 

ments  (i  896-1 901)  on  the  Bionomics  of  South  African  Insects,  chiefly  directed  to 

the  Investigation  of  Mimicry  and  Warning  Colours.     Trans.  Ent.  Soc.  London, 
pp.  287-584,  pis.  9-23. 
Shelford,  R.     1902.     Observations  on  some  Mimetic  Insects  and  Spiders  from  Borneo  and 

Singapore.     Proc.  Zool.  Soc.  London,  1902,  vol.  2,  pp.  230-284,  pis.  19-23. 
Weismann,  A.     1902.     Vortrage  iiber  Descendenztheorie.     2  vols.     12  +  456  pp.,  95  figs.; 

6  -f-  462  pp.,  3  pis.,  36  figs.     Jena.     G.  Fischer.     See  pp.  103-133. 
Piepers,  M.  C.     1903.     Mimikry,  Selektion  und  Darwinismus.     452  pp.     Leiden.     E.  J. 

Brill. 
Poulton,  E.  B.     1903.     Experiments  in  1893,  1894  and  1896  upon  the  colour- relation  be- 
tween  lepidopterous  larvae  and  their  surroundings,  and  especially  the  effect  of 


LITERATURE  4OI 

lichen-covered  bark  upon  Odontopera   bidentata,   Gastropacha  quercifolia,  etc. 

Trans.  Ent.  Soc.  London,  pp.  311-374,  pis.  16-18. 
Packard,  A.  S.     1904.     The  Origin  of  the  Markings  of  Organisms  (Poecilogenesis)  due  to  the 

Physical  rather  than  to  the  Biological  Environment;  with  Criticisms  of  the  Bates- 

Miiller  Hypothesis.     Proc.  Amer.  Phil.  Soc,  vol.  43,  pp.  393-450.* 
Marshall,  G.  A.  K.     1908.     On  Diaposematism,  with  Reference  to  Some  Limitations  of  the 

Miillerian  Hypothesis  of  Mimicry.     Trans.  Ent.  Soc.  London,  pp.  93-142. 
Zugmayer,     E.     1908.     Ueber     Mimikry     und    verwandte    Erscheinungen.     Zeits.  wiss. 

Zool,  bd.  90,  pp.  313-326. 
Dewar,  D.,  and  Finn,  F.     1909.     The  Making  of  Species.     19  +  400  pp.,  15  pis.     London, 

John  Lane.     New  York,  John  Lane  Co. 
Eltringham  H.     1909.     An  .\ccount  of  Some  E.xperiments  on  the  Edibility  of  Certain 

Lepidopterous  Larva;.     Trans.  Ent.  Soc.  London,  pp.  471-478. 
Marshall,  G.  A.  K.     1909.     Birds  as  a  Factor  in  the  Production  of  Mimetic  Resemblances 

among  Butterflies.     Trans.  Ent.  Soc.  London,  pp.  329-383. 
Moulton,  J.  C.     1909.     On  Some  of  the  Principal  Mimetic  (Miillerian)    Combinations  of 

Tropical  American  Butterflies.     Trans.  Ent.  Soc.  London,  1908,  pp.    585-606, 

pis.  30-34- 
Poulton,  E.B.     1909.     Mimetic  North  American  Species  of  the  Genus  Limenitis.     Trans. 

Ent.  Soc.  London,  1908,  pp.  447-488,  pi.  25. 
Thayer,  A.  H.     1909.     An  Arraignment  of  the  Theories  of  Mimicry  and  Warning  Colors. 

Pop.  Sc.  Mon.,  vol.  75,  pp.  550-570. 
Eltringham,   H.     1910.     African    Mimetic    Butterflies.     4  +  136   pp.,    10   pis.     Oxford. 
Punnett,  R.  C.     1910.     "Mimicry"  in  Cejdon  Butterfl:ies,  with  a  Suggestion  as  to  the; 

Nature  of  Polymorphism.     Spolia  Zeylanica,  vol.  7,  pp.  1-24,  pis.  i,  2. 
Bridges,  E.     1911.     Experiments  in  1909  and  1910  upon  the  Colour  Relation  between 

Lepidopterous  Larvas  and  Pupae  and  their  Surroundings.     Trans.  Ent.  Soc.  London , 

pp.  136-147- 
McAtee,  W.  L.     1912.     The  Experimental  Method  of  Testing  the  Efficiency  of  Warning 

and  Cryptic  Coloration  in  Protecting  Animals  from  their  Enemies.     Proc.  Acad. 

Nat.  Sc.  Phila.,  vol.  64,  281-364.* 
Mandus,  N.     1912.     A  Study  of  Mimicry   (Batesian  and  Miillerian)   by  Temperature 

Experiments  on  Two  Tropical  Butterfl.ies.     Trans.  Ent.  Soc.  London,  pp.   445- 

469,  pi.  41- 
Jacobi,    A,     1913.     Mimikry    und    verwandte    Erscheinungen.     9  +  215    pp.,    31    figs. 

Braunschweig.     Friedr.  Vieweg  &  Sohn. 
Abbott,  J.  F.     1914.     Mimicry  in  the  Genus  Limenitis  with  Especial  Reference  to  the 

"Poulton  Hypothesis."     Washington  Univ.  Studies,  vol.  i,  pp.  203-221,  2 -figs., 

I  pi. 
Punnett,  R.  C.     1915.    Mimicry  in  Butterflies.    6  +  188  pp.,  16  pis.  Cambridge.    University 

Press. 
Eltringham,  H.     1916.     On  Specific  and  Mimetic  Relationships  in  the  Genus  Heliconius, 

L.     Trans.  Ent.  Soc.  London,  pp.  101-148,  pis.  11-17. 
Gerould,  J.  H.     1916.     Mimicry  in  Butterflies.     Amer.  Nat.,  vol.  50,  pp.  184-192. 
Yoimg,   R.   T.     1916.     Some  Experiments  on  Protective  Coloration.     Journ.  Exp.  Zool., 

vol.  20,  pp.  457-507,  8  figs.,  3  pis.* 
Carpenter,  G.  D.     1921.     Experiments  on  the  Relative  Edibility  of  Insects,  with  Special 

Reference  to  Their  Coloration.     Trans.  Ent.  Soc.  London,  pp.  1-105. 

INSECTS  IN  RELATION  TO  PLANTS 

Darwin,  C.     1877.     The  Effects  of^Cross  and  Self  Fertilisation  in  the  Vegetable  Kingdom. 
8  +  482  pp.     New  York.     D.  Appleton  &  Co. 


462  ENTOMOLOGY 

Lubbock,  J.     1882.     On  British  Wild  Flowers  considered  in  Relation  to  Insects.     Ed.  4. 

16  +  186  pp.,  130  figs.     London.     Macmillan  &  Co. 
Muller,  H,     1883.     The  Fertilisation  of  Flowers.     12+669  pp.,  186  figs.     London.     Mac- 
millan &  Co. 
Darwin,  C.     1884.     The  Various  Contrivances  by  which  Orchids  are  fertilised  by  Insects. 

Ed.  2.     16  +  300  pp.,  38  figs.     New  York.     D.  Appleton  &  Co. 
Darwin,    C.     1884.     Insectivorous    Plants.     10  +  462    pp.,    30    figs.     New    York.     D. 

Appleton  &  Co. 
Forbes,  S.  A.     1886.     Studies  on  the  Contagious  Diseases  of  Insects.     Bull.  111.  St.  Lab. 

Nat.  Hist.,  vol.  2,  pp.  257-321,  i  pi. 
Thaxter,  R.     1888.     The  Entomophthoreae  of  the  United  States.     Mem.  Bost.  Soc.  Nat. 

Hist.,  vol.  4,  pp.  133-201,  pis.  14-21. 
Robertson,  C.     1889-99.     Flowers  and  Insects.     I-XIX.     Bot.  Gaz.,  vols.  14-22,  25,  28. 
Seitz,A.     1890,1893,1894.     Allgemeine  Biologie  der  Schmetterlinge.     Zool.  Jahrb.,  Abth. 

Syst.,  etc.,  bd.  5,  pp.  281-343;  bd.  7,  pp.  131-186,  823-851.* 
Eckstein,  K.     1891.     Pflanzengallen  und  Gallentiere.     88  pp.,  4  taf.     Leipzig.     R.  Freese. 
Robertson,  C.     1891-96.     Flowers  and  Insects.     Trans.  Acad.  Sc,  St.  Louis,  vols.  5-7. 
Cooke,  M.  C.     1892.     Vegetable  Wasps  and  Plant  Worms.     5  +  364  pp.,  4  pis.,  51  figs. 

London. 
Riley,  C.  V.     1892.     Some  Interrelations  of  Plants  and  Insects.     Proc.  Biol.  Soc.  Wash., 

vol.  7,  pp.  81-104,  figs.  1-15. 
Riley,   C.  V.     1892.     The  Yucca  Moth  and  Yucca  Pollination.     Third  Ann.   Rept.  Mo. 

Bot.  Garden,  pp.  99-158,  pis.  34-43- 
Moller,  A.     1893.     Die  Pilzgarten  einiger  siidamericanischer  Ameisen.  •  Bot.  Mitt,  aus  den 

Tropen,  heft  6.     7  +  127  pp.,  7  taf.,  4  figs.     Jena.     G.Fischer. 
Trelease,  W.     1893.     Further  Studies  of  Yuccas  and  their  Pollination.     Fourth  Ann. 

Rept.  Mo.  Bot.  Garden,  pp.  181-226,  pis.  1-23. 
Adler,  H.,  and  Straton,  C.  R.     1894.     Alternating  Generations.     A  Biological  Study  of 

Oak  Galls  and  Gall  Flies.     40  +  198  pp.,  3  pis.     Oxford.     Clarendon  Press.* 
Webster,  F.  M.     1894.     Vegetal  Parasitism  among  Insects.     Journ.  Columbus  Hort.  Soc, 

pp.  1-19,  pis.  3-5,  figs.  I,  2. 
Heim,  F.  L.     1898.     The  Biologic  Relations  between  Plants  and  Ants.     Ann.  Rept.  Smiths. 

Inst.  1896,  pp.  411-455,  pis.  17-22.     Trans,  from  Compt.  rend.  24me  Sess.  Ass. 

fr.  I'av.  Sc.  189s,  pp.  31-75- 
Schimper,  A.  F.  W.     1898.     Pflanzen-Geographie  auf  physiologischer  Grundlage.     18  + 

876  pp.,  502  figs.,  5  plates,  4  maps.     Jena.     G.  Fischer.     (See  pp.  147-170.)* 

Trans:  1903.     W.   R.   Fischer.     Plant-Geography  upon  a  Physiological  Basis. 

30  +  839  pp.,  502  figs.,  4  maps.     Oxford,  Clarendon  Press.     (See  pp.  126-156.)* 
Needham,  J.  G.     1900.     The  Fruiting  of  the  Blue  Flag  (Iris  versicolor  L.) .    Amer.  Nat., 

vol.  34,  pp-  361-386,  pi.  I,  figs.  1-4. 
Gibson,  W.H.     1901.     Blossom  Hosts  and  Insect  Guests.     19  +  197  pp.,  figs.     New  York. 

Newson  &  Co. 
Connold,  E.  T.     1902.     British  Vegetable  Galls.     12  +  312  pp.,  130  pis.,  10  figs.     New 

York.     E.  P.  Dutton  &  Co. 
CookjM.T.     1902-04.     Galls  and  Insects  Producmg  Them.     Pts.  MX.     Ohio  Nat.,  vols. 

2-4,  pis.     Same,  Bull.  Ohio  St.  Univ.,  ser.  6,  no.  15;  ser.  7,  no.  20;  ser  8,  no.  13. 
Needham,  J.  G.     1903.     Button-Bush  Insects.     Psyche,  vol.  10,  pp.  22-31. 
Cowan,  T.  W.     1904.     The  Honey  Bee:  its  Natural  History,  Anatomy  and  Physiology. 

Ed.  2.     12  +  220  pp.,  73  figs.     London.     Houlston  &  Sons.* 
Rossig,  H.     1904.     Von  welchen  Organen  der  Gallwespenlarven  geht  der  Reiz  zur  Bildung 

der  Pflanzengalle  aus?     Zool.  Jahrb.,  Abth.  Syst.,  etc.,  bd.   20,   pp.    19-90,   taf. 
i-6.* 


LITERATURE  463 

Chadwick,   G.  H.     1908.     Catalogue  of  the  "Phytoptid  '  Galls  of  North  America.     In 

Bull.  N.  Y.  State  Mus.,  no.  124,  pp.  1 18-155.* 
Casteel,  D.  B.     1912.     The  Manipulation  of  the  Wa.x  Scales  of  the  Honey  Bee.     Circ.  161, 

U.  S.  Dept.  Agr.,  Bur.  Ent.     13  pp.,  7  figs. 
Casteel,  D.  B.     1912.     The  Behavior  of  the  Honey  Bee  in  Pollen  Collecting.     Bull.  121, 

U.  S.  Dept.  Agr.,  Bur.  Ent.     36  pp.,  9  figs.* 
Cosens,A.     1912.     A  Contribution  to  the  Morphology  and  Biology  of  Insect  Galls.     Trans. 

Canadian  Inst.,  vol.  9,  pp.  297-387,  13  pis.,  9  figs. 
Thompson,  S.  M.     1915.     An  Illustrated  Catalogue  of  American  Insect  Galls.     116  pp., 

21  pis.     Ed.  by  E.  P.  Felt.     R.  I.  Hospital  Trust  Co.     Nassau,  Rensselaer  Co., 

N.  Y. 
Felt,  E.  P.     1917.     Key  to  American   Insect  Galls.     Bull.   N.  Y.  State  Mus.,  no.    200. 

310  pp.,  250  figs.,  16  pis.* 
Rand,  F.  V.,  and  Pierce,  W.  D.     1920.     A  coordination  of  our  knowledge  of  insect  trans- 
mission in  plant  and  animal  diseases.     Phytopathology,  vol.  10,  pp.  189-231.* 

INSECTS  IN  RELATION  TO  OTHER  ANIMALS 

Aughey,  S.     1878.     Notes  on  the  Nature  of  the  Food  of  the  Birds  of  Nebraska.     First 

Rept.  U.  S.  Ent.  Comm.,  Appendix  2,  pp.  13-62. 
Forbes,  S.  A.     1878.     The  Food  of  Illinois  Fishes.     Bull.  111.  St.  Lab.  Nat.  Hist.,  vol.  i,  no. 

2,  pp.  71-89. 
Forbes,  S.  A.     1880.     The  Food  of  Birds.     Trans.  111.  St.  Hort.  Soc,  vol.  13  (1879),  pp. 

120-172. 
Forbes,  S.  A.     1880.     On  Some  Interactions  of  Organisms.     Bull.  111.  St.  Lab.  Nat.  Hist., 

vol.  I,  no.  3,  pp.  3-17. 
Forbes,  S.  A.     1880.     The  Food  of  Fishes.     Bull.  111.  St.  Lab.  Nat.  Hist.,  vol.  i,  no.  3,  pp. 

18-65. 
Forbes,  S.  A.     1880.     On  the  Food  of  Young  Fishes.     Bull.  111.  St.  Lab.  Nat.  Hist.,  vol.  i, 

no.  3,  pp.  66-79. 
Forbes,  S.  A.     1880.     The  Food  of  Birds.     Bull.  111.  St.  Lab.  Nat.  Hist.,  vol.  i,  no.  3,  pp. 

80-148. 
Forbes,  S.  A.     1883.     The  Regulative  Action  of  Birds  upon  Insect  Oscillations.     Bull. 

111.  St.  Lab.  Nat.  Hist.,  vol.  i,  no.  6,  pp.  3-32. 
Forbes,  S.  A.     1883.     The  Food  of  the  Smaller  Fresh- Water  Fishes.     Bull.  111.  St.  Lab. 

Nat.  Hist.,  vol.  i,  no.  6,  pp.  65-94. 
Forbes,  S.  A.     1883.     The  First  Food  of  the  Common  White-Fish.     Bull.  111.  St.  Lab.  Nat. 

Hist.,  vol.  I,  no.  6,  pp.  95-109. 
Dimmock,  G.     1886.     Belostomidae  and  some  other  Fish-destroying  Bugs.     Ann.  Rept. 

Fish  Game  Comm.  Mass.,  pp.  67-74,  i  fig.* 
Forbes,  S.  A.     1888.     Studies  on  the  Food  of  Fresh- Water  Fishes.     Bull.  111.  St.  Lab.  Nat. 

Hist,  vol.  2  pp.  433-473- 
Forbes,  S.  A.     1888.     On  the  Food  Relations  of  Fresh- Water  Fishes:  a  Summary  and 

Discussion.     Bull.  111.  St.  Lab.  Nat.  Hist.,  vol.  2,  pp.  475-538. 
Wilcox,  E.V.     1892.     The  Food  of  the  Robin.     Bull.  Ohio  Agr.  Exp.  Sta.,  no.  43,  pp.  115- 

131- 
Beal,  F.  E.  L.     1897.     Some  Common  Birds  in  their  Relations  to  Agriculture.     Farmer's 

Bull.  U.  S.  Dept.  Agric,  no.  54,  pp.  1-40,  figs.  1-22. 
Kirkland,  A.  H.     1897.     The  Habits,  Food  and  Economic  Value  of  the  American  Toad. 

Bull.  Hatch  Exp.  Sta.  Mass.  Agr.  Coll.,  no.  46,  pp.  3-30,  pi.  2. 
Judd,  S.  D.     1899.     The  EflBciency  of  Some  Protective  Adaptations  in  Securing  Insects 

from  Bir  ds.     Amer.  Nat.,  vol.  33,  pp.  461-484. 


464  ENTOMOLOGY 

Palmer,  T.  S.     19C0.     A  Review  of  Economic  Ornithology.     Yearbook  U.  S.  Dept.  Agric. 

1899,  pp.  259-292. 
Judd,  S,  D.     1901.     The  Food  of  Nestling  Birds.     Yearbook  U.  S.  Dept.  Agric.  1900,  pp. 

411-436,  pis.  49-53,  figs.  48-56. 
Forbes,  S.  A.     1903.     Studies  of  the  Food  of  Birds,  Insects  and  Fishes.     Second  Ed.     Bull. 

111.  St.  Lab.  Nat.  Hist.,  vol.  i,  no.  3. 
Weed,  C.  M.,  and  Dearborn,  N.     1903.     Birds  in  their  Relations  to  Man.     8  +  380  pp., 

figs.     Philadelphia  and  London.     J.  B.  Lippincott  Co.* 
Washburn,   F.   L.     1918.     Injurious   Insects  and  Useful  Birds.  18  +  453  pp.,  414  figs., 

4  pis.     Philadelphia  and  London.     J.  B.  Lippincott  Co. 
Undefhill,  B.  M.     1920.     Parasites  and  Parasitosis  of  the  Domestic  Animals.     19  +  379 

pp.,  172  figs.,  8  pis.     New  York.     The  Macmillan  Co. 

INSECTS  IN  RELATION  TO  DISEASES 

Kanthack,  A.  A.,  Durham,  H.  E.,  and  Blandford,  W.  F.  H.     1898.     On  Nagana,  or  Tsetse 

fly  disease.     Proc.  Roy.  Soc.  Lond.,  vol.  64,  pp.  100-118. 
Finlay,  C.  J.     1899.     Mosquitoes  considered  as  Transmitters  of  Yellow  Fever  and  Malaria. 

Psyche,  vol.  8  pp.  379-384. 
Nuttall,  G.  H.  F.     1899.     On  the  role  of  Insects,  Arachnids  and  Myriapods,  as  carriers  in 

the  spread  of  Bacterial  and  Parasitic  Diseases  of  Man  and  Animals.     A   Critical 

and  Historical  Study.  Johns  Hopk.  Hosp.  Rept.,  vol.  8,  no.  i,  154  pp.,  3  pis. 
Ross,  R.  1899.  Life-History  of  the  Parasites  of  Malaria.  Nature,  vol.  60,  pp.  322-324. 
Chiisly,  C.     1900.     Mosquitoes  and  Malaria:  a  summary  of  knowledge  on  the  subject  up 

to  date;  with  an  account  of  the  natural  history  of  mosquitoes.     9  +  80  pp.,  5  pis. 

London. 
Howard,  L.  O.     1900.     Notes  on  the  Mosquitoes  of  the  United  States:  giving  some  account 

of  their  structure  and  biology,  with  remarks  on  remedies.     Bull.  U.  S.  Dept.  Agric, 

Div.  Ent.,  no.  25  (n.  s.),  70  pp.,  22  figs. 
Howard,  L.  O.     1900.     A  contribution  to  the  study  of  the  insect  fauna  of  human  excrement 

(with  especial  reference  to  the  spread  of  typhoid  fever  by  flies) .     Proc.  Wash.  Acad. 

Sc,  vol.  2,  pp.  541-604,  pis.  30,  31,  figs.  17-38. 
Ross,  R.     1900.     Malaria  and  Mosquitoes.     Nature,  vol.  61,  pp.  522-527. 
Ross.  R.,  and  Fielding-Otild,  R.     1900.     Diagrams  illustrating  the  Life-history  of  the 

Parasites  of  Malaria.     Quart.  Journ.  Micr.  Sc,  vol.  43  (n.  s.),  pp.  571-579,  pis.  30, 

31- 
Grassi,  B.     1901.     Die  Malaria-Studien  eines  Zoologen.     8  +  250  pp.,  8  taf.     Jena.     G. 

Fischer. 
Howard,  L.  O.     1901.     ^Mosquitoes;  how  they  live;  how  they  carry  disease;  how  they  are 

classified;  how  they  may  be  destroj^ed.     15  -f-  241  pp.,  50  figs.,  i  pi.     New  York. 

McClure,  Phillips  &  Co. 
Sternberg,  G.  M.     1901.     The  Transmission  of  Yellow  Fever  by  Mosquitoes.     Pop.  Sc. 

Mon.,  vol.  59,  pp.  225-241. 
■Howard,  L.  O.    1902.     Insects  as  Carriers  and  Spreaders  of  Disease.     Year-book  U.  S. 

Dept.  Agric.  1901,  pp.  177-192,  figs.  5-20. 
Braxm,  M.     1903.     Die  thierischen   Parasiten  des  Menschen.     Rev.  Ed.     12-1-360  pp., 

272  figs.     Wiirzburg. 
Sternberg,  G.  M.     1903.     Infection  and  Immunity;  with  special  Reference  to  the  Preven- 
tion of  Infectious  Diseases.     5  +  293  pp.,  12  figs.     New  York  and  London.     G.  P. 

Putman's  Sons. 
Blanchard,  R.     1905.    Les  ]\Ioustiques,  histoire  naturelle  et  medicale.     673  pp.,  316  figs. 

Paris.     De  Rudeval. 


LITERATURE  465 

Austen,  E.  E.     1903.     A  Monograph  of  the  Tsetse  FHes.     9  +  319  pp.,  9  pis.     London. 

British  Museum. 
Braun,  M.     1906.     The  Animal  Parasites  of  Man.     Trans.  Sambon  and  Theobald.      19  + 

453  PP->  294  figs.     New  York.     Wm.  Wood  &  Co. 
Bruce,  D.     1907.     Trypanosomiasis.-    In  Osier's  Modern  Medicine,  vol.  i,  pp.    460-487, 

tigs.  31-34,  pi.  4.     Philadelphia  and  New  York.     Lea  Bros.  &  Co. 
Calvert,  W.  J.     1907.     Plague.     In    Osier's    Modern    Medicine,    vol.     2,    pp.     760-780. 

Philadelphia  and  New  York.     Lea  Bros.  &  Co. 
Carroll,  J.     1907.     Yellow   Fever.     In  Osier's  Modern  Medicine,  vol.   2,  pp.   736-759. 

Philadelphia  and  New  York.     Lea  Bros.  &  Co. 
Craig,  C.  F.     1907.     The  Malarial  Fevers.     In  Osier's  Modern  Medicine,  vol.  i,  pp.  392- 

448,  figs.  26-30,  pis.  1-3.     Philadelphia  and  New  York.     Lea  Bros.  &  Co. 
Griinberg,  K.     1907.     Die  blutsaugenden  Dipteren.     6  +  188  pp.     Jena.     G.  Fischer. 
Jackson,  T.W.     1907.     Tropical    Medicine.     8  +  536    pp.,    106   figs.     Philadelphia.     P. 

Blakiston's  Son  &  Co. 
Laveran,  A.,  and   Mesnil,  F.     1907.     Trypanosomes  and  Trypanosomiases.     Trans.  D. 

Nabarro.     19  +  538  pp.,   81   figs.,    i   pi.     London.     Bailliere,   Tindall   &    Co.* 
Mitchell,  E.  G.     1907.     Mosquito  Life.     22  +  281  pp.,  54  figs.     New  York  and  London. 

G.  P.  Putnam's  Sons. 
Stephens,  J.  W.  W.,  and  Christophers,  S.  R.     1908.     The  Practical  Study  of  Malaria  and 

Other  Blood  Parasites.     Ed.  3.     18  +  414  pp.,  128  figs.     London.     Williams  and 

Norgate. 
Boyce,  R.  W.     1909.     Mosquito  or  Man?     The  Conquest  of  the  Tropical  World.      16  + 

267  pp.,  44  figs.     London.     John  Murray. 
Calkins,  G.  N.     1909.     Protozoology.     9  +  349  PP-,   125   figs.,  4  pis.     New  York  and 

Phila.    Lea  &  Febiger.* 
Thimm,  C.  A.     1909.     Bibliography  of  Trypanosomiasis.     22S  pp.     London.     ^^Sleeping 

Sickness  Bureau. 
Braun,  M.,  and  Liihe,  M.     1910.     A  Handbook  of  Practical  Parasitology.     Tr.  L.  Forster. 

8  +  208  pp.,  100  figs.     London.     John  Bale,  Sons  &  Danielsson. 
Doane,  R.  W.     1910.     Insects  and  Disease.     14  +227  pp.,  112  figs.,  i   pi.     New  York. 

Henry  Holt  &  Co.* 
Austen,  E.E.     1911.     A  Handbook  of  the  Tsetse-flies  (Genus  Glossina).     10  +  no  pp.,  24 

figs.,  10  pis.     London.     British  Museum. 
Doane,  R.  W.     1911,  1912.     An  Annotated  List  of  the  Literature  on  Insects  and  Disease. 

Journ.  Econ.  Ent.,  vol.  4,  pp.  386-398;  vol.  5,  pp.  268-285. 
Howard,  L.  O.     1911.     The  House  Fly;  Disease  Carrier.     19  +  312  pp.,  40  figs.,   r  pi. 

New  York.     F.  A.  Stokes  Co.* 
Manson,    P.     1911.     Tropical    Diseases.     Ed.    6.     22  +  968    pp.,    254    figs.,    15    pis. 

London  and  New  York.     Cassell  &  Co. 
Reed,  W.,  Carroll,  J.,  Gorgas,  W.  C,  and  others.     1911.     Yellow  Fever;  a  Compilation  of 

Various  Publications.     Doc.  No.  822,  U.  S.  Senate,  6ist  Congress.     250  pp.,  7  figs., 

5  pis.     Washington.     Govt.  Printing  Office. 
Brues,  C.  T.     1913.     The  Relation  of  the  Stable  Fly  (Stomoxys  calcitrans)  to  the  Trans- 
mission of  Infantile  Paralysis.     Journ.  Econ.  Ent.,  vol.,  6,  pp.  101-109. 
Herms,  W.  B.     1915.     Medical  and  Veterinary  Entomology.     12  +  393  PP-.  228  figs. 

New  York.     The  Macmillan  Co. 
Riley,  W.  A.,  and  Johannsen,  O.  A.     1915.     Handbook  of  Medical  Entomology.      9  +  348 

pp.,  174  figs.     Ithaca,  N.  Y.     Comstock  Pub.  Co.* 
Chandler,  A.  C.     1918.     Animal  Parasites  and  Human  Disease.     13  +  570  pp.,  254  figs. 

New  York.     John  Wiley  &  Sons,  Inc.* 


466  ENTOMOLOGY 

Pierce,  W.  D.     1921.     Sanitary  Entomology,  Entomology  of  Disease,  Hygiene  and  Sanita- 
tion.    26  +  518  pp.,  88  figs.     Boston.     R.  G.  Badger.* 

INTERRELATIONS  OF  INSECTS 

Van  Beneden,  P.  J.     1876,     Animal  Parasites  and  Messmates.     28  +  274  pp.,  83  figs. 

New  York.     D.  Appleton  &  Co. 
McCook,  H.  C.     1877.     Mound-making  Ants  of  the  Alleghenies,  their  Architecture  and 

Habits.     Trans.  Amer.  Ent.  Soc,  vol.  6,  pp.  253-296,  figs.  1-13. 
Fabre,  J.  H.     1879-1905.     Souvenirs  entomologiques.     Etudes  sur  I'instinct  et  les  moeurs 

des  insectes.     9  Series.     Paris.     C.  Delagrave.     Trans,  of  Ser.  I:  1901.     Fatre, 

J.  H.     Insect  Life.     12  +  320  pp.,  16  pis.     London  and  New  York.     The  Mac- 

millan  Co 
Forbes,  S.  A.     1880.     Notes  on  Insectivorous  Coleoptera.     Bull.  111.  St.  Lab.  Nat.  Hist., 

vol.  I,  no.  3,  pp.  153-169.     Second  Ed.,  1903. 
McCook,  H.  C.     1880.     The  Natural  History  of  the  Agricultural  Ant  of  Te.xas.     310  pp., 

24  pis.     Philadelphia.     J.  B.  Lippincott  &  Co. 
Webster,  F.  M.     1880.     Notes  upon  the  Food  of  Predaceous  Beetles.     Bull.  111.  St.  Lab. 

Nat.  Hist.,  vol.  i,  no.  3,  pp.  149-152.     Second  Ed.,  1903. 
McCook,  H.  C.     1881.     Note  on  a  new  Northern  Cutting  Ant,  Atta  septentrionalis.     Proc. 

Acad.  Nat.  Sc.  Phila.  1880,  pp.  359-363,  i  fig. 
McCook,  H.  C.     1881.     The  Shining  Slavemaker.     Notes  on  the  Architecture  and  Habits 

of  the  American  Slave-making  Ant,  Polyergus  lucidus.     Proc.  Acad.  Nat.  Sc. 

Phila.  1880,  pp.  376-384,  pi.  19. 
Lubbock,  J.     1882,  1902,  1904.     Ants,  Bees  and  Wasps.     19  +  448  pp.,  31  figs.,  5  pis. 

New  York.     D.  Appleton  &  Co. 
McCook,  H.  C.     1882.     The  Honey  Ants  of  the  Garden  of  the  Gods,  and  the  Occident  Ants 

of  the  American  Plains.     188  pp.,  13  pis.     Philadelphia.     J.  B.  Lippincott  &  Co. 
Forbes,  S.  A.     1883.     The  Food  Relations  of  the  Carabidae  and  Coccinellidae.     Bull.  111. 

St.  Lab.  Nat.  Hist.,  vol.  i,  no.  6,  pp.  33-64. 
Cheshire,  F.  R.     1886.     Bees  and  Bee-keeping.     2  vols.     Vol.  i,  7  +  336  pp.,  8  pis.,  71 

figs;  vol.  2,  652  pp.,  127  figs.,  I  pi.     London.     L.  Upcott  Gill. 
Seitz,  A.     1890, 1893, 1894.     Allgemeine  Biologie  der  Schmetterlinge.     Zool.  Jahrb.,  Abth. 

Syst.,  etc.,  bd.  5,  pp.  281-343;  bd.  7,  pp.  131-186,  823-851.* 
Verhoeff,  C.     1892.     Beitrage  zur  Biologie  der  Hymenoptera.     Zool.  Jahrb.,  Abth.  Syst., 

etc.,  bd.  6,  pp.  680-754,  taf.  30,  31. 
Wasmann,    E.     1894.     Kritisches    Verzeichnis    der    myrmekophUen    und    termitophilen 

Arthropoden.     231  pp.     Berlin.     F.  L.  Dames. 
Grassi,  B.,  and  Sandias,  A.     1896-97.     The  Constitution  and  Development  of  the  Society 

of  Termites,  etc.     Trans,  by  W.  F.  H.  Blandford.     Quart.  Journ.  Micr.  Sc,  vol. 

39,  pp.  245-322,  pis.  16-20;  vol.  40,  pp.  1-75. 
Janet,  C.     1896.    Les  Fourmis.     Bull.  Soc.  zool.  France,  vol.  21,  pp.  60-93.     Sep.,  37  pp. 

Paris. 
Howard,  L.  O.     1897.     A  Study  in  Insect  Parasitism.     Bull.  U.  S.  Dept.  Agric,  Div.  Ent., 

tech.  ser.  no.  5,  pp.  1-57,  figs.  1-24. 
Peckham,  G.  W.,  and  E.  G.     1898.     On  the  Instincts  and  Habits  of  the  Solitary  Wasps. 

Bull  Wis.  Geol.  Nat.  Hist.  Surv.,  no.  2,  sc.  ser.  no.  i,  4  +  245  pp.,  14  pis. 
Wasmann,  E.     1898,     Die  Gaste  der  Ameisen  und  Termiten.     Illustr.  Zeits.  Ent.,  bd.  3, 

I  taf. 
Benton,  F.     1899.     The  Honey  Bee:  A  Manual  of  Instruction  in  Apiculture.     Bull.  U.  S. 

Dept.  Agric,  Div.  Ent.,  no.  1  (n.  s.),  pp,  1-118,  pis.  i-n,  figs.  1-76.* 
Fielde,  A.  M.     1901.     A  Study  of  an  Ant.     Proc.  Acad.  Nat.  Sc.  Phila.,  vol.  53,  pp.  425- 

449- 


LITERATURE  467 

Fielde,  A.  M.     1901.     Further  Study  of  an  Ant.     Proc.  Acad.  Nat.  Sc.  Phila.,  vol.  53,  pp. 

521-544- 
Wheeler,  W.  M.     1901.     The  Compound  and  Mixed  Nests  of  American  Ants.    Amer.  Nat. , 

vol.  35,  pp.  4.31,  513,  701,  791,  figs.  1-20. 
Enteman,  M.  M.     1902.     Some  Observations  on  the  Behavior  of  the  Social  Wasps.     Pop. 

Sc.  Men.,  vol.  61,  pp.  339-351- 
Fielde,  A.M.     1902.     Notes  on  an  Ant.     Proc.  Acad.  Nat.  Sc.  Phila.,  vol.  54,  pp.  599-625. 
Dickel,  F.     1903.     Die   Ursachen  der  geschlechtlichen   DifTerenzirung  im   Bienenstaat. 

Archiv.  ges.  Phys.,  bd.  95,  pp.  66-106,  fig.  i. 
Fielde,  A.  M.     1903,     Supplementary  Notes  on  an  Ant.     Proc.  Acad.  Nat.  Sc.  Phila.,  vol. 

55.  PP-  491-495- 
Heath,  H.     1903.     The  Habits  of  California  Termites.     Biol.  Bull.,  vol.  4,  pp.  47-63,  figs. 

1-3- 
Janet,  C.     1903.     Observations  sur  les  guepes.     85  pp.,  30  figs.     Paris.     C.  Naud. 
Melander,  A.  L.,  and  Brues,  C.  T.     1903.     Guests  and  Parasites  of  the  Burrowing  Bee 

Halictus.     Biol.  Bull.,  vol.  5,  pp.  1-27,  figs.  1-7. 
Fielde,  A.  M.     1904.     Power  of  Recognition  among  Ants.     Biol.  Bull,  vol.  7,  pp.  227-250, 

4  figs- 
Fielde,  A.  M.,  and  Parker,  G.  H.     1904.     The  Reactions  of  Ants  to  Material  Vibrations. 

Proc.  Acad.  Nat.  Sc.  Phila.,  vol.  56,  pp.  642-650.* 
Wheeler,  W.  M.     1904.     A  New  Type  of  Social  Parasitism  among  Ants.     Bull.  Amer. 

Mus.  Nat.  Hist.,  vol.  20,  pp.  347-375. 
Emery,  C.     1904.     Zur  Kenntniss  des  Polymorphismus  der  Ameisen.     Zool.  Jahrb.,  Sup- 
plement, bd.  7,  pp.  587-610,  6  figs. 
Forel,  A.     1904.     Ueber  Polymorphismus  und  Variation  bei  den  Ameisen.     Zool.  Jahrb., 

Supplement,  bd.  7,  pp.  571-586. 
Peckham,  G.  W.,  and  E.  G.     1906.     Wasps,  Social  and  Solitary.     15  +  311  pp.     Boston 

and  New  York.     Houghton,  Mifflin  &  Co. 
Holmgren,  N.     1906.     Studien  liber  sudamerikanische  Termiten.     Zool.   Jahrb.,   Abt. 

Anat.  Ont.,  bd.  23,  pp.  521-676,  81  figs.* 
Wheeler,  W.  M.     1906.     The  Habits  of  the  Tent-building  Ant  (Cremastogaster  lineolata 

Say).     Bull.  Amer.  Mus.  Nat.  Hist.,  vol.  22,  pp.  1-18,  pis.  1-6. 
Wheeler,  W.  M.     1906.     On  the  Founding  of  Colonies  by  Queen  Ants,  etc.     Bull.  Amer. 

Mus.  Nat.  Hist.,  vol.  22,  pp.  33-105,  pis.  8-14. 
Wheeler,  W.  M.     1907.     The  Polymorphism  of  Ants,  with  an  Account  of  Some  Singular 

Abnormalities  due  to  Parasitism.     Bull  Amer.  Mus.  Nat.  Hist.,  vol.  23,  pp.  1-93, 

pis.  1-6. 
Wheeler,  W.  M.     1907.     The  Fungus-growing  Ants  of  North  America.     Bull.  Amer.  Mus. 

Nat.  Hist.,  vol.  23,  pp.  669-807,  pis.  49-53,  31  figs.* 
Pricer,  J.  L.     1908.     The  Life  History  of  the  Carpenter  Ant.     Biol.  Bull,  vol.  14,  pp.  177- 

218,  figs.  1-7.* 
Donisthorpe,  J.  K.     1910.     Some  Experiments  with  Ants'   Nests.     Trans.    Ent.   Soc. 

London,  pp.  142-150. 
Wheeler,  W.  M.     1910.     Ants;  their  Structure,  Development  and  Behavior.     25  +  663 

pp.,  286  figs.,  I  pi.     New  York.     Columbia  Univ.  Press.* 
Crawley,  W.  C.     1912.     Parthenogenesis  in  Worker  Ants,  with  Special  Reference  to  Two 

Colonies  of  Lasius  niger  Linn.     Trans.  Ent.  Soc.  London,  191 1,  pp.  657-663.* 
Sladen,  F.  W.  L.     1912.     The  Humble-Bee,  its  Life-History  and  How  to  Domesticate  it. 

13  -1-  283  pp.,  34  figs.,  6  pis.     London.     Macmillan  &  Co. 
Fuller,  C.     1915.     Observations  on  Some  South  African  Teimites.     Ann.  Natal  Mus., 

vol.  3,  pp.  329-504,  16  figs.,  pis.  25-35. 


468  ENTOMOLOGY 

Thompson,  C.  B.     1917.     Origin  of  the  Castes  of  the  Common  Termite,  Leucotermes 

flavipes  Kol.     Journ.  Morph.,  vol.  30,  pp.  83-153,  8  pis.* 
Wheeler,  W.  M.     1918.     A  study  of  some  ant  larvae,  with  a  consideration  of  the  origin  and 

meaning  of  the  social  habit  among  insects.     Proc.  Amer.  Phil.  Soc,  vol.  57,  pp. 

293-343,  12  figs. 
Thompson,  C.  B.     1919.     The  Development  of  the  Castes  of  Nine  Genera  and  Thirteen 

Species  of  Termites.     Biol.  Bull.,  vol.  36,  pp.  379-398. 
Thompson,  C.  B.,  and  Snyder,  T.  E.     1919.     The  Question  of  the  Phylogenetic  Origin  of 

the  Termite  Castes.     Biol.  Bull.,  vol.  36,  pp.    1 15-132. 
Wheeler,  W.  M.     1919.     The  parasitic  Aculeata,  a  study  in  evolution.     Proc.  Amer.  Phil. 

Soc,  vol.  58,  pp.  1-40. 
Banks,  N.,  and  Snyder,  T.  E.     1920.     .\  Revision  of  the  Nearctic  Termites,  with  Notes  on 

Biology  and  Geographic  Distribution.     Bull.  U.  S.  Nat.  Mus.,  no.  108,  8  +  228 

pp.,  70  figs.,  35  pis.* 
Wheeler,  W.  M.     1921.     A  Study  of  Some  Social  Beetles  in  British  Guiana  and  of  Their 

Relations  to  the  Ant-plant  Tachigalia.     Zoologica,  vol.  3,  pp.  35-126,  5  pis.* 

INSECT  BEHAVIOR 

Pouchet,  G.     1872.     De  I'influence  de  la  lumiere  sur  les  larves  de  dipteres  privees  d'  organes 

e.xterieurs  de  la  vision.     Rev.  Mag.  Zool,  ser.  2,  t.  23,  pp.  110-117,  etc.,  pis.  12-16. 
Fabre,  J.  H.     1879-1905.     Souvenirs  entomologiques.     Etudes  sur  I'instinct  et  les  moeurs 

des  insectes.     9  Series.     Paris.     C.  Delagrave.     Trans,  of  Ser.  I:  1901.     Fabre, 

J.  H.      Insect  Life.     12  +320  pp.,  16  pis.     London  and  New  York.     The  Mac- 

millan  Co. 
Lubbock,  J.     1882,  1884.     Ants,  Bees  and  Wasps.     19  +  448  pp.,  31  figs.,  5  pis.     New 

York.     D.  Appleton  &  Co. 
Graber,  V.     1884.     Grundlinien  zur  Erforschung  des  Helligkeits-  und  Farbensinnes  der 

Tiere.     8  +  322  pp.     Prag  und  Leipzig. 
Romanes,  G.  J.     1884.     Animal  Intelligence.     14  +  520  pp.     New  York.     D.  Appleton 

&  Co. 
Lubbock,  J.     1888.     On  the  Senses,  Instincts  and  Intelligence  of  Animals,  with  Special 

Reference  to  Insects.     29  +  292  pp.,  118  figs.     New  York.     D.  Appleton  &  Co. 
Plateau,  F.     1889.     Recherches  e.xperimentales  sur  la  Vision  chez  les  Arthropodes.     Mem. 

cour.  Acad.  roj-.  Belgique,  t.  43,  pp.  1-91. 
Eimer,  G.  H.  T.     1890.     Organic  Evolution  as  the  Result  of  the  Inheritance  of  Acquired 

Characters  according  to  the  Laws  of  Organic  Growth.     28  +  435  pp.     Trans,  by 

J.  T.  Cunningham.     London  and  New  York.     Macmillan  &  Co. 
Loeb,  J.     1890.     Der  Heliotropismus  der  Thiere  und  seine  Uebereinstimmung  mit  dem 

Heliotropismus  der  Pflanzen.     118  pp.     Wiirzburg. 
Seitz,  A.     1890.     Allgemeine  Biologie  der  Schmetterlinge.     Zool.  Jahrb.,  Abth.  Syst.,  bd. 

5,  pp.  281-343. 
Exner,  S.     1891.     Die  Physiologie  der  facettirten  Augen  von  Krebsen  und  Insecten.     8  + 

206  pp.,  8  taf.,  23  figs.     Leipzig  und  Wien. 
Loeb,  J.     1891.     Ueber  Geotropismus  bei  Thieren.     Arch.  ges.  Phys.,  bd.  49,  pp.  175-189, 

figs. 
Morgan,  C.  Lloyd.     1891.     Animal  Life  and  Intelligence.     13  +  512  pp.,  40  figs.    Boston. 

Ginn  &  Co. 
James,  W.     1893.     The  Principles  of  Psychology.     2  vols.     18  +  1393  pp.,  94  figs.      New 

'   York.     Henry  Holt  &  Co. 
Loeb,  J.     1893.    Ueber  kunstliche  Umwandlung  positiv  heliotropischer  Thiere  in  negativ 

heliotropische  und  umgekehrt.     Arch.  ges.  Phys.,  bd.  54,  pp.  81-107. 


LITERATURE  469 

Baldwin,  J.  M.     1896.     Heredity  and  Instinct.     Science,  vol.  3  (n.  s.),  pp.  438-441,  558- 

561. 
Morgan,  C.  Lloyd,  1896.     Habit  and  Instinct.     351   pp.     London  and  New  York.     E. 

Arnold. 
Davenport,  C.  B.     1897,  1899.     E.xperimental  Morphology.     2  Pts.     32   +  508  pp,  140 

figs.     New  York  and  London.     The  Macmillan  Co. 
Loeb,   J.     1897.     Zur   Theorie   der  physiologischen  Licht-   und   Schwerkraftwirkungen. 

Arch.  ges.  Phys.,  bd.  64,  pp.  439-466. 
Bethe,  A.     1898.     Durfen  wir  den  Ameisen  und  Bienen  psychische  Qualitaten  zuschreiben? 

Archiv  ges.  Phys.,  bd.  70.  pp.  15-110,  taf.  i,  2,  5  figs. 
Peckham,  G.  W.,  and  E.  G.     1898.     On  the  Instincts  and  Habits  of  the  Solitary  Wasps. 

Bull.  Wis.  Geol.  Nat.  Hist.  Surv.,  no.  2,  so.  ser.  no.  i.     4  +  245  pp.,  14  pis. 
Verwom,  M.     1899.     General  Physiology.     An  Outline  of  the  Science  of  Life.     Trans. 

by  F.  S.  Lee.     16  +  615  PP->  285  figs.     London  and  New  York.     Macmillan  &  Co. 
Wasmann,  E.     1899.     Die  psychischen  Fahigkeiten  der  Ameisen.     Zoologica,  heft   26. 

6  +  132  pp.,  3  taf.     Stuttgart.     E.  Nagele. 
Wheeler,  W.  M.    1899.    Anemotropism  and  Other  Tropisms  in  Insects.    Arch.  Entw.  Org., 

bd.  8,  pp.  373-381. 
Whitman,  C.  O.     1899.     Animal  Behavior.     Biol  Lect.,  Marine  Biol.  Lab.,  Woods  Hole, 

Mass.,  1898,  pp.  285-338.     Boston.     Ginn  &  Co. 
Loeb,  J.     1900.     Comparative  Physiology  of  the  Brain  and  Comparative  Psychology.     309 

pp.,  39  figs.     New  York,  G.  P.  Putnam's  Sons.     London,  J.  Murray.* 
Morgan,    C.   Lloyd.     1900.     Animal    Behaviour.     8  +  344   pp.,    26   figs.     London.     E. 

Arnold. 
Radl,  E.     1901.      Ueber  den  Phototropismus  einiger  Arthropoden.     Biol.  Centralb.,  bd. 

21,  pp.  75-86. 
Radl,  E.     1901.     Untersuchungen  iiber  die  Lichtreactionen  der  Arthropoden.     Arch.  ges. 

Phys.,  bd.  87,  pp.  418-466. 
Enteman,  M.  M.     1902.     Some  Observations  on  the  Behavior  of  the  Social  Wasps.     Pop. 

Sc.  Mon.,  vol.  61,  pp.  339-351- 
Weismann,  A.     1902.     Vortrage  iiber  Descendenztheorie.     2  vols.     12  +  456  pp.,  95  figs.; 

6  +  462  pp.,  3  pis.,  36  figs.     Jena.     G.  Fischer.     See  pp.  159-181. 
Kathariner,  L.     1903.     Versuche  iiber  die  Art  der  Orientierung  bei  der  Honigbiene.    Biol. 

Centralb.,  bd.  23,  pp.  646-660,  i  fig. 
Morgan,  T.  H.     1903.     Evolution  and  Adaptation.     13  +  470  pp.,  5  figs.     New  York  and 

London.     The  Macmillan  Co. 
Parker,  G.  H.    1903.    The  Phototropism  of  the  Mourning-cloak  Butterfly,  Vanessa  antiopa 

Linn.     Mark  Anniv.  Vol.,  pp.  453-469,  pi.  ^s-* 
Fielde,  A.  M.,  and  Parker,  G.  H.     1904.     The  Relations  of  Ants  to  Material  Vibrations. 

Proc.  Acad.  Nat.  Sc.  Phila.,  vol.  56,  pp.  642-650.* 
Forel,  A.     1904.     The  Psychical  Faculties  of  Ants  and  some  other  Insects.     Ann.  Rept. 

Smiths.  Inst.  1903,  pp.  587-599.     Trans,  from   Proc.  Fifth  Intern.  Zool.  Congr. 

Berlin,  1901,  pp.  141-169. 
Jennings,  H.  S.     1904.     Contributions  to  the  Study  of  the  Behavior  of  Lower  Organisms. 

256  pp.,  81  figs.     Carnegie  Inst.  Washington.* 
Carpenter,  F.  W.     1905.     The  Reactions  of  the  Pomace  Fly  (Drosophila  ampelophila 

Loew)  to  Light,  Gravity  and  Mechanical  Stimulation.     Amer.  Nat.,  vol.  39,  pp. 

157-171.* 
Hartman,  C.     1906.     Observations  on  the  Habits  of  some  Solitary  Wasps  of  Texas.     Bull. 

•     Univ.  Texas,  no.  65,  sc.  ser.  no.  7,  pp.  1-73,  4  pis. 
Holmes,  S.  J.     1905.     The  Reactions  of  Ranatra  to  Light.     Journ.  Comp.  Neur.  Psych., 

vol.  15,  pp.  305-349,  figs.  1-6. 


470  ENTOMOLOGY 

Loeb,  J.  1905.     Studies  in  General  Physiology.      2  vols.     24  +  782  pp.,  162  figs.     Univ. 

Chicago  Decenn.  Publ.,  ser.  2,  vol.  15,  pts.  i,  2. 
Wasmann,  E.     1905.     Comparative  Studies  in  the  Psychology  of  Ants  and  of  Higher  Ani- 
mals.    10  +  200  pp.     St.  Louis  and  Freiburg,  B.  Herder;  London  and  Edinburgh, 

Sands  &  Co.* 
Holmes,  S.  J.     1906.     Death-feigning  in  Ranatra.     Journ.  Comp.  Neur.  Psych.,  vol.  16, 

pp.  200-216. 
Barrows,  W.  M.     1907.     The  Reactions  of  the  Pomace  Fly,  Drosophila  ampelophila  Loew, 

to  Odorous  Substances.     Journ.  Exp.  Zool.,  vol.  4,  pp.  515-537,  figs.  1-5. 
Buckingham,  E.  N.     1911.     Division  of  Labor  Among  Ants.     Proc.  Amer.  Acad.  Arts. 

Sc,  vol.  46,  pp.  425-507,  I  pi.* 
Herms,  W.  B.     1911.     The  Photic  Reactions  of  Sarcophagid  Flies,  etc.     Journ.  Exp.  Zool., 

vol.  10,  pp.  167-226,  figs.  1-25.* 
Mast,  S.  O.     1911.    Light  and  the  Behavior  of  Organisms.     11 -f- 410  pp.,  35  figs.     New 

York.     John  Wiley  &  Sons.* 
Severin,  H.  H.  P.  and  H.  C.     1911.    An  Experimental  Study  on  the  Death-Feigning  of 

Belostoma    (Zaitha    Aucct.)  flumineum    Say  and  Nepa  apiculata  Uhler.     Be- 
havior Monogr.,  vol.  i,  no.  3,  44  pp.,  i  pi.* 
Gee,  W.  P.,  and  Lathrop,  F,  H.    1912.    Death  Feigning  in  Conotrachelus  nenuphar  Herbst. 

Ann.  Ent.  Soc.  Amer.,  vol.  5,  pp.  391-399,  i  fig.* 
Patten,  B.  M.     1914.     A  Quantitative  Determination  of  the  Orienting  Reaction  of  the 

Blowfly  Larva  (Calliphora  erythrocephala  Meigen).     Journ.  E.xp.  Zool.,  vol.  17, 

pp.  213-280,  figs.  1-24.* 
Dolley,  W.  L.,  Jr.     1916.     Reactions  to  light  in  Vanessa  antiopa,  with  special  reference  to 

circus  movements.     Journ.  Exp.  Zool.,  vol.  20,  pp.  357-420,  figs.  1-21.* 
Loeb,  J.,  and  Wasteneys,  H.     1916.    The  Relative  Efficiency  of  Various  Parts  of  the  Spec- 
trum for  the  Heliotropic  Reactions  of  Animals  and  Plants.     Journ.  Exp.  Zool., 

vol.  20,  pp.  217-236,  6  figs. 
Cole,  W.  H.     1917.     The  Reactions  of  Drosophila  ampelophila  Loew  to  Gravity,  Centrifu- 

gation,  and  Air  Currents.     Journ.  Anim.  Behav.,  vol.  7,  pp.  71-80.* 
Mclndoo,  N.  E.     1917.     Recognition  Among  Insects.     Smiths.  Misc.  Coll.,  vol.  68,  no. 

2,  78  pp.* 
Bouvier,  E.  L.     1918.    La  Vie  psychique  des  Insectes.     300  pp.,  16  figs.     Paris.      Ernest 

Flammarion.* 
Lodge,  O.  C.     1918.     An  Examination  of  the  Sense-reactions  of  Flies.     Bull.  Ent.  Res., 

vol.  9,  pp.  141-151,  4  pis. 
Loeb,  J.    1918.    Forced  Movements,  Tropisms,.  and  Animal  Conduct.    209  pp.,  42  figs. 

Philadelphia.     J.  B.  Lippincott  Co.* 
Rau,   P.    and  N.      1918.      Wasp    Studies  Afield.     372  pp.,  68  figs.  Princeton,  N.  J. 

Princeton.  Univ.  Press. 
Howes,  P.  G.     1919.     Insect     Behavior.     176  pp.,  many  pis.     Boston.     R.  G.  Badger. 
Riley,  C.  F.  C.      1921.      Responses  of  the  Large  Water-Strider,  Gerris  remigis  Say,  to 

Contact  and  Light.     Ann.  Ent.  Soc.  Amer.,  vol.  14,  pp.  231-289,  figs.  1-12.* 

GEOGRAPHICAL  DISTRIBUTION 

Darwin,  C.  1859,1869.  On  the  Origin  of  Species  by  means  of  Natural  Selection.  Pp- 
II  +440.     New  York.     D.  Appleton  &  Co.     See  pp.  302-357. 

LeConte,  J.  L.  1859.  The  Coleoptera  of  Kansas  and  Eastern  New  Mexico.  Smithson. 
Contrib.,  vol.  11,  6  -|-  58  pp.,  2  pis.,  map. 

Bates,  H.  W.  1864.  The  Naturalist  on  the  River  Amazons.  12  -|-  466  pp.,  figs.  London. 
J.  Murray. 


LITERATURE  47I 

Wallace,  A.  R.     1865.     On  the  Phenomena  of  Variation  and  Geographical  Distribution  as 

illustrated  by  the  Papilionidae  of  the  Malayan  Region.     Trans.  Linn.  Soc.  Zool., 

vol.  25,  pp.  1-71,  pis.  1-8. 
"Wallace,  A.  R.     1869.     The  Malay  Achipelago.     12  +  638  pp.,  51  figs.,  10  maps.     New 

York.     Harper  &  Bros. 
Murray,  A,     1873.     On  the  Geographical  Relations  of  the  Chief  Coleopterous  Faunae. 

Journ.  Linn.  Soc.  Zool,  vol.  11,  pp.  1-89. 
Belt,  T.     1874,  1888.     The  Naturalist  in  Nicaragua.     32  +  403  PP-j  figs.    London.     J. 

MuTTa.y;  E.  Bumpus. 
Wallace,  A.  R.     1876.     The  Geographical  Distribution  of  Animals.     2  vols.     Vol.  i,  21  + 

503  pp.,  13  pis.,  5  maps;  vol.  2,  8  +  607  pp.,  7  pis.,  2  maps.     New  York.      Harper 

&  Bros. 
Semper,  K.     1881.      Animal  Life  as  affected  by  the  Natural  Conditions  of  Existence.    1 6  + 

472  pp.,  106  figs.,  2  maps.     New  York.     D.  Appleton  &  Co. 
Wallace,  A.  R.     1881.     Island  Life,  or  the  Phenomena  and  Causes  of  Insular  Faunas  and 

Floras,  etc.     16  +  522  pp.,  26  maps  and  figs.     New  York.     Harper  &  Bros. 
Gill,  T.     1884.     The  Principles  of  Zoogeography.     Proc.  Biol.  Soc.  Wash.,  vol.  2,  pp.  1-39. 
Forbes,  H.  O.     1886.     A  Naturalist's  Wanderings  in  the  Eastern  Archipelago.     19  +  S36 

pp.,  figs.,  pis.,  maps.     New  York.     Harper  &  Bros. 
Schwarz,  E.  A.     1888.     The  Insect  Fauna  of  Semitropical  Florida,  with  Special  Regard  to 

the  Coleoptera.     Ent.  Amer.,  vol.  4,  pp.  165-175. 
Merriam,  C.  H.     1890.     Results  of  a  Biological  Survey  of  the  San  Francisco  Mountain 

Region  and  Desert  of  the  Little  Colorado,  Arizona.     U.  S.  Dept.  Agric,  Div. 

Ornith.  Mamm.,  N.  A.  Fauna,  no.  3.     6  +  136  pp.,  13  pis.,  5  maps,  2  figs. 
Schwarz,  E.  A.     1890.     On  the  Coleoptera  common  to  North  America  and  other  Countries. 

Proc.  Ent.  Soc.  Wash.,  vol.  i,  pp.  182-194. 
Seitz,A.     1890,1893,1894.     AUgemeine  Biologic  der  Schmetterlinge.     Zool.  Jahrb.,  Abth. 

Syst,  etc.,  bd.  5,  pp.  281-343;  bd.  7,  pp.  131-186,  823-851.* 
Trouessart,  E.  L.     1890.    La  Geographie  Zoologique.     11  +338  pp.,  63  figs.,  2  maps. 

Paris. 
Wallace,  A,  R.     1890.     A  Narrative  of  Travels  on  the  Amazon  and  Rio  Negro,  etc.     Ed.  3. 

14  +  363  pp.,  16  pis.     London,  New  York  and  Melbourne.     Ward,  Lock  &  Co. 
Bates,  H.  W.     1892.     The  Naturalist  on  the  River  Amazons.     Reprint.     89  +  395  pp., 

figs.     London.     J.  Murray. 
Distant,  W.  L.     1892.     A  Naturalist  in  the  Transvaal.     16  +  277  pp.,  pis.  figs.    London. 

R.  H.  Porter. 
Hudson,  W.H.     1892.     The  Naturalist  in  La  Plata.     8  +  388  pp.,  figs.    London.     Chap- 
man &  Hall. 
Webster,  F.  M.     1892.     Modern  Geographical  Distribution  of  Insects  in  Indiana.     Proc. 

Ind.  Acad,  Sc,  pp.  81-88,  map. 
Merriam,  C.  H.     1893.     The  Geographic  Distribution  of  Life  in  North  American,  with 

special  Reference  to  the  Mammalia.     Smithson.  Rept.  1891,  pp.  365-415.     From 

Proc.  Biol.  Soc.  Wash.,  vol.  7,  pp.  1-64. 
Elwes,  H.  J.     1894.     The  Geographical  Distribution  of  Butterflies.     Trans.  Ent.  Soc. 

London,  Proc,  pp.  52-84. 
Hamilton,  J.     1894.     Catalogue  of  the  Coleoptera  common  to  North  America,  Northern 

Asia  and  Europe,  with  Distribution  and  Bibliography.     Trans.  Amer.  Ent.  Soc, 

vol.  21,  pp.  345-416  +  19. 
Merriam,  C.  H.     1894.     Laws  of  Temperature  Control  of  the  Geographic  Distribution  of 

Terrestrial  Animals  and  Plants.     Nat.  Geogr.  Mag.,  vol.  6,  pp.  229-238,  3  maps. 
Scudder,  S.  H.     1894.     The  Effect  of  Glaciation  and  of  the  Glacial  Period  on  the  Present 

Fauna  of  North  America.     Amer.  Journ.  Sc,  sen  3,  vol.  48,  pp.  179-187. 


472  ENTOMOLOGY 

Webster,  F.  M.     1894.     Some  Insect  Immigrants  in  Ohio.     Bull.  Ohio  Agr.  Exp.  Sta., 

ser.  2,  vol.  6,  no.  51  (1893),  pp.  118-129,  figs.  17,  18. 
Whymper,  E.     1894.     Travels  amongst  the  Great  Andes  of  the  Equator.     24  +  456  pp., 

20  pis.,  4  maps,  118  figs.     New  York.     C.  Scribner's  Sons.     1891.     Suppl.  Ap- 
pendix.    22  +  147  pp.,  figs.     London.     J.  Murray. 
Beddard,  F.  E.     1895.     A  Text-book  of  Zoogeography.     8-1-246  pp.,  5  maps.     Cambridge, 

England.     University  Press. 
Howard,  L.  O.     1895.     Notes  on  the  Geographical  Distribution  within  the  United  States 

of  certain  Insects  injuring  Cultivated  Crops.     Proc.  Ent.  Soc.  Wash.,  vol.  3,  pp. 

219-226. 
Webster,  F.  M.     1895.     Notes  on  the  Distribution  of  some  Injurious  Insects.     Proc.  Ent. 

Soc.  Wash.,  vol.  3,  pp.  284-290. 
Webster,  F.  M.     1896.     The  Probable  Origin  and  Diffusion  of  Blissus  leucopterus  and 

Murgantia  histrionica.     Journ.  Cine.  Soc.  Nat.  Hist.,  vol.  18,  pp.  141-155,  fig.  i, 

pl-  5. 
Carpenter,  G.  H.     1897.     The  Geographical  Distribution  of  Dragon-flies.     Proc.  Roy. 

Dublin  Soc,  vol.  8,  pp.  439-468,  pl.  17. 
Heilprm,  A.     1897.     The  Geographical  and  Geological  Distribution  of  Animals.     12-1-435 

pp.,  map.     New  York.     D.  Appleton  &  Co. 
Sairille-Kent,  W.     1897.     The  Naturalist  in  Australia.     15  +  302  pp.,  50  pis.,  104  figs. 

London.     Chapman  &  Hall. 
Webster,  F.  M.     1897.     Biological  Effects  of  Civilization  on  the  Insect  Fauna  of  Ohio. 

Fifth  Ann.  Rept.  Ohio  St.  Acad.  Sc,  pp.  32-46,  2  figs. 
Merriam,  C.  H.     1898.    Life  Zones  and  Crop  Zones  of  the  United  States.     Bull.  U.  S. 

Dept.  Agric,  Div.  Biol.  Surv.,  no.  10,  pp.  1-79,  map. 
Webster,  F.  M.     1898.     The  Chinch  Bug.     Bull.  U.  S.  Dept.  Agric,  Div.  Ent.,  no.  15 

(n.  s.),  82  pp.,  19  figs.     (See  pp.  66-82.) 
Semon,  R.     1899.     In  the  Australian  Bush  and  on  the  Coast  of  the  Coral  Sea,  etc.     15  -f- 

552  pp.,  4  maps,  86  figs.     London  and  New  York.     Macmillan  &  Co. 
Tower,  W.  L.     1900.     On  the  Origin  and  Distribution  of  Leptinotarsa  decem-lineata  Say, 

and  the  Part  that  some  of  the  Climatic  Factors  have  played  in  its  Dissemination. 

Proc.  Amer.  Ass.  Adv.  Sc,  vol.  49,  pp.  225-227. 
Adams,  C.  C.     1902.     Postglacial  Origin  and  Migrations  of  the  Life  of  tlie  Northeastern 

United  States.     Journ.  Geogr.,  vol.  i,  pp.  303-310,  352-357;  rnap. 
Adams,  C.  C.     1902.     Southeastern  United  States  as  a  Center  of  Geographical  Distribution 

of  Flora  and  Fauna.     Biol.  Bull,  vol.  3,  pp.  115-131.* 
Tutt,  J.  W.     1902.     The  Migration  and  Dispersal  of  Insects.     132  pp.     London.     E.  Stock. 
Webster,  F.  M.     1902.     The  Trend  of  Insect  Diffusion  in  North  America.     Thirty-second 

Ann.  Rept.  Ent.  Soc.  Ontario  (1901),  pp.  63-67,  maps  1-3. 
Webster,  F.  M.     1902.     Winds  and  Storms  as  Agents  in  the  Diffusion  of  Insects.     Amer. 

Nat.,  vol.  36,  pp.  795-801. 
Webster,  F.  M.     1903.     The  Diffusion  of  Insects  in  North  America.     Psyche,  vol.  10,  pp. 

47-58,  pl.  2. 
Jacobi,  A.     1904.     Tiergeographie.     152  pp.,  2  maps.     Leipzig. 
Morse,  A.  P.     1904.     Researches  on  North  American  Acridiidae.     Publ.  No.  18,  Carnegie 

Inst.  Wash.     55  pp.,  8  pis.,  13  figs. 
Adams,  C.  C.     1909.     The  Coleoptera  of  Isle  Royale,  Lake  Superior,  and  their  Relation  to 

the  North  American  Centers  of  Dispersal.     In  Adams'  Ecol.  Survey.     Rept.  Univ. 

Mich.  Mus.,  pp.  157-191. 
Shelford,  V.  E.     1911.     Physiological  Animal  Geography.     Journ.  Morph.,  vol.  22,  pp. 

551-618,  19  figs. 
Shamion,  H.  J.     1915.     Do  Insects  Migrate  Like   Birds?     Harper's  Mag.,   Sept.,   pp. 

609-618,  7  figs. 


LITERATURE  473 

GEOLOGICAL  DISTRIBUTION 

Herr,  O.     1847-53.     Die  Insectenfauna  der  Tertiargebilde  von  ffiningen  und  von  Radoboj 
in  Croatien.     3  Th.     644  pp.,  40  taf.     Leipzig.     From  Neue  Denks.  schweiz. 
Gesell.  Naturw.,  bd.  8,  11,  13. 
Scudder,  S.  H.     1880.     The  Devonian  Insects  of  New  Brunswick.     Ajin.  Mem.  Bost.  See. 

Nat.  Hist.,  41  pp.,  I  pi. 
Scudder,  S.  H.     1882.     A  Bibliography,  of  Fossil  Insects.     Bibl.  Contrib.  Libr.  Harv.  Univ. , 

no.  13.     47  pp.     Cambridge,  Mass.* 
Scudder,  S.  H.     1885.     The  Earliest  Winged  Insects  of  America:  a  Re-e.xamination  of  the 
Devonian  Insects  of  New  Brunswick,  etc.     8  pp.,  i  pi.,  2  figs.     Cambridge,  Mass. 
Scudder,  S.  H.     1885.     Systematische  Uebersicht  der  fossilen  Myriopoden,  Arachnoideen 
und  Insekten.     In  K.  A.  Zittel:  Handbuch  der  Palaeontologie,  abth.  i,  bd.  2,  pp. 
721-831,  figs.  894-1109.     Trans.  190c:     C.  R.  Eastman.     Text-Book  of  Palaeon- 
tology, vol.  I,  pp.  682-691,  figs.  ir4i-i476.     London  and  New  York.     Macmillan 
&  Co.* 
Scudder,  S.  H.     1886.     The  Cockroach  of  the  Past.     In  L.  C.  Miall  and  A.  Denny:  The 
Structure  and  Life-History  of  the  Cockroach,  pp.  205-220,  figs.  1 19-1 25.     London 
and  Leeds.* 
Scudder,  S.  H.     1886.     Systematic  Review  of  our  Present  Knowledge  of  Fossil  Insects. 

Bull.  U.  S.  Geol.  Surv.,  no.  31,  128  pp.     Washington. 
Scudder,  S.  H.     1889.     The  Fossil  Butterflies  of  Florissant.     Eighth  Ann.  Rept.  Dir.  U.  S. 

Geol.  Surv.,  pp.  433-474,  pi.  53.     Washington. 
Scudder,  S.  H.     1890.     The  Work  of  a  Decade  upon  Fossil  Insects.     Psyche,  vol.  5,  pp. 

287-295. 
Scudder,  S.  H.     1890,     A  Classed  and  Annotated  Bibliography  of  Fossil  Insects.     Bull. 

U.  S.  Geol.  Surv.,  no.  69,  loi  pp.     Washington.* 
Scudder,  S.  H.     1890.     The  Tertiary  Insects  of  North  America.     U.  S.  Geol.  Surv.  Terr., 

vol.  13,  734  pp.,  28  pis.,  I  map,  3  figs.     Washington. 
Scudder,  S.  H.     1891.     Index  to  the  Known  Fossil  Insects  of  the  World,  including  Myria- 

pods  and  Arachnids.     Bull.  U.  S.  Geol.  Surv.,  no.  71,  744  PP-     Washington.* 
Scudder,  S.  H.     1892.     Some  Insects  of  Special  Interest  from  Florissant,  Colorado,  and 
other  Points  in  the  Territories  of  Colorado  and  Utah.     Bull.  U.  S.  Geol.  Surv.,  no. 
93,  35  PP-,  3  pls-     Washington. 
Scudder,  S.  H.     1893.     Insect  Fauna  of  the  Rhode  Island  Coal  Field.     Bull.  U.  S.  Geol. 

Surv.,  no.  loi,  27  pp.,  2  pis.     Washington. 
Scudder,  S.  H.     1893.     The  American  Tertiary  Aphidse,  with  a  List  of  the  Known  Species 
and  Tables  for  their  Determination.     Thirteenth  Ann.  Rept.  U.  S.  Geol.  Surv.,  pt. 
2,  pp.  341-372,  pis.  102-106.     Washington. 
Scudder,  S.  H.     1893.     Tertiary  Rhynchophorous  Coleoptera  of  the  United  States.     Mon- 

ogr.  U.  S.  Geol.  Surv.,  vol.  21,  11  -f  206  pp.,  12  pis.     Washington. 
Brongniart,  C.     1894.     Recherches  pour  servir  a  I'histoire  des  insectes  fossiles  des  temps 

primaires,  etc.     2  vols.     537  pp.,  37  pis.     St.  Etienne. 
Scudder,  S.  H.     1894.     Tertiary  Tipulidse,  with  Special  Reference  to  those  of  Florissant, 

Colorado.     Proc.  Amer.  Phil.  Soc,  vol.  32,  83  pp.,  9  pis. 
Scudder,  S.  H.     1896.     Revision  of  the  American  Fossil  Cockroaches,  with  Descriptions  of 

New  Forms.     Bull.  U.  S.  Geol.  Surv.,  no.  124,  176  pp.,  12  pis.     Washington. 
Goss,  H.     1900.     The  Geological  Antiquity  of  Insects.     Ed.  2.     4  +  52  PP.     London. 

Gurney  &  Jackson.* 
Scudder,  S.  H.     1900.     Adephagous  and  Clavicorn  Coleoptera  from  the  Tertiary  Deposits 
at  Florissant,  Colorado,  etc.     Monogr.  U.  S.  Geol.  Surv.,  vol.  40,  148  pp-,  n  pls. 
Washington. 


474  ENTOMOLOGY 

Scudder,  S.  H.     1900.     Canadian  Fossil  Insects.     4.  Additions  to  the  Coleopterous  Fauna 

of  the  Interglacial  Clays  of  the  Toronto  District,  etc.     Contrib.  Can.  Pal.,  Geol. 

Surv.  Can.,  vol.  2,  pp.  67-92,  pis.  6-15.     Ottawa. 
Handlirsch,  A.     1908.     Die  Fossilen  Insekten  und  die  Phylogenie  der  Rezenten  Formen. 

Ein  Handbuch  fur  Palaontologen  und  zoologen.     49  +  1430  pp.,  14  fig?.,  51  pis., 

etc.     Leipzig.     W.  Engelman.* 
Handlirsch,  A.     1920,1921.     Palaeontologie.     In  Schroder:  Handbuch  der  Entomologie, 

bd.  3,  pp.  117-306,  figs.  52-237.* 

INSECT  ECOLOGY 

Davenport,  C.  B.     1897,  1899.     Experimental  Morphology.     2  Pts.     29  +  508  pp.,  140 

figs.     New  York  and  London.     The  Macmillan  Co.* 
Chittenden,  F.  H.     1900.     Insects  and  the  Weather:  Observations  During  the  Season  of 

1899.     Bull.  U.  S.  Dept.  Agric,  Div.  Ent.,  no.  22  (n.  s.),  pp.  51-64. 
Morgan,  T.  H.     1903.     Evolution  and  Adaptation.     13  +  470  pp.,  7  figs.     New  York. 

The  Macmillan  Co. 
Morse,  A.  P.     1904.     Researches  on  North  American  Acridiidae.     55  pp.,  13  figs.,  8  pis. 

Carnegie  Inst.     Washington. 
Clements,  F.  E.     1905.     Research  Methods  in  Ecology.     17  +  334  pp.,  85  figs.    Lincoln, 

Neb.     University  Pub.  Co.* 
Hart,  C.  A.,  and  Gleason,  H.  A.     1907.     On  the  Biology  of  the  Sand  Areas  of  Illinois. 

BuU.  111.  State  Lab.  Nat.  Hist.,  vol.  7,  pp.  137-272,  pis.  8-23.* 
Herms,  W.  B,     1907.     An  Ecological  and  Experimental  Study  of  Sarcophagidae  with 

Relation  to  Lake  Beach  Debris.     Journ.  Exp.  2k)ol.,  vol.  4,  pp.  45-83,  7  figs.* 
Morgan,   T.  H.     1907.     Experimental  Morphology.     12  +  454  pp.,  25  figs.     New  York. 

The  Macmillan  Co. 
Morse,  A.  P.     1907.     Further  Researches  on  North  American  Acridiidse.     54  pp.,  9  pis.. 

Carnegie  Inst.     Washington. 
Shelford,  V.  E.     1907.     Preliminary  Note  on  the  Distribution  of  the  Tiger  Beetles  (Cicin- 

dela)and  its  Relation  to  Plant  Successsion.     Biol.  Bull.,  vol.  14,  pp.  9-14. 
Sanderson,  E.  D.     1908.     The  Relation  of  Temperature  to  the  Hibernation  of  Insects. 

Journ.  Econ.  Ent.,  vol.  i,  pp.  56-65,  2  figs. 
Sanderson,  E.  D.     1908.     The  Influence  of  Minimum  Temperatures  in  Limiting  the 

Northern  Distribution  of  Insects.     Journ.  Econ.  Ent.,  vol.  i,  pp.  245-262,  7  maps. 
Warming,  E.     1909.     Oecology  of  Plants.     An  Introduction  to   the  Study  of  Plant- 
Communities.     II  +422  pp.     Oxford.     Clarendon  Press.* 
Bachmetjew,  P.     1910.     Experimentelle  entomologische  Studien.     10  +  944  +  108  pp.. 

31  figs.     Leipzig.     W.  Engelmann. 
Sanderson,  E,  D.     1910.     The  Relation  of  Temperature  to  the  Growth  of  Insects.     Journ . 

Econ.  Ent.,  vol.  3,  pp.  1 13-140,  figs.  6-26.* 
Doten,  S.  B.     1911.     Concerning  the  Relation  of  Food  to  Reproductive  Activity  and 

Longevity  in  Certain  Hymenopterous  Parasites.     Techn.  Bull.  Agr.  Exp.  Sta. 

Univ.  Nevada,  no.  78,  30  pp.,  10  pis. 
Shelford,  V.  E.     1911.     Ecological  Succession.     III.     A  Reconnaissance  of  its  Causes  in 

Ponds  with  Particular  Reference  to  Fish.     Biol.  Bull.,  vol.  22,  pp.  1-38.* 
Watson,  J.  R.     1911.     A  Contribution  to  the  Study  of  the  Ecological  Distribution  of  the 

Animal  Life  of  North  Central  New  Mexico,  with  Especial  Attention  to  the  Insects. 

Rept.  No.   I,  Natural  Resources  Survey,  Conservation  and  Natural  Resources 

Commission,  New  Mexico,  pp.  67-117.     Santa  Fe,  N.  M.     New  Mexican  Print- 
ing Co. 
Riley,  C.  F.  C.     1912.     Observations  on  the  Ecology  of  Dragon-fly  Nymphs:  Reactions  to 

Light  and  Contact.     Ann.  Ent.  Soc.  Amer.,  vol.  5,  pp.  273-292.* 


LITERATURE  475 

Shelford,  V.  E.     1912.     Ecological  Succession.     IV.  Vegetation  and  the  Control  of  Land 

Animal  Communities.     Biol.  Bull.,  vol.  23,  pp.  59-99,  figs.  1-6.* 
Shelford,  V.  E.     1912.     Ecological  Succession.     V.     Aspects  of  Physiological  Classifica- 
tion.    Biol.  Bull.,  vol.  23,  pp.  331-370.* 
Adams,  C.  C.     1913.     Guide  to  the  Study  of  Animal  Ecology.     12  +  183  pp.,  7  figs.     New 

York.     The  Macmillan  Co.* 
Cameron,  A.  E.     1913.     General  Survey  of  the  Insect  Fauna  of  the  Soil  within  a  Limited 

Area  near  Manchester.     Journ.  Econ.  Biol.,  vol.  8,  pp.  159-204,  2  pis.*  ' 
Headlee,  T.  J.     1913.     Some  Facts  Regarding  the  Influence  of  Temperature  and  Moisture 

Changes  on  the  Rate  of  Insect  Metabolism.     Science,  n.  s.,  vol.  36,  p.  310. 
Shelford,  V.  E.     1913.     Animal  Communities  in  Temperate  America.     A  Study  in  Animal 

Ecology.     13+362    pp.,    306    figs.,    9    diagrams,    2    maps.     Chicago.     Univ. 

Chicago  Press.* 
Shelford,  V.  E.     1913.     The  Reactions  of  Certain  Animals  to  Gradients  of  Evaporating 

Power  of  Air.    A  Study  in  Experimental  Ecology.     Biol.  Bull.,vol.  25,  pp.  79-120.* 
Vestal,  A.  G.     1913.    Local  Distribution  of  Grasshoppers  in  Relation  to  Plant  Associations. 

Biol.  Bull.,  vol.  25,  pp.  141-180,  I  fig.* 
Vestal,  A.  G.     1913.     An  Associational  Study  of  Illinois  Sand  Prairie.     Bull.  111.  State  Lab. 

Nat.  Hist.,  vol.  10,  pp.  1-96,  pis.  1-5.* 
Baxmiberger,  J.  P.     1914.     Studies  in  the  Longevity  of  Insects.     Ann.  Ent.  Soc.  Amer., 

vol.  7,  pp.  323-353-* 
Headlee,  T.  J.     1914.     Some  Data  on  the  Effect  of  Temperature  and  Moisture  on  the  Rate 

of  Insect  Metabolism.     Journ.  Econ.  Ent.,  vol.  7,  pp.  413-417. 
Krogh,  A.     1914.     On  the  influence  of  the  temperature  on  the  rate  of  embryonic  develop- 
ment.    Zeits.  allgem.  Phys.,  bd.  16,  pp.  163-177,  figs.  1-8. 
Krogh,  A.     1914.     On  the  rate  of  development  and  CO2  production  of  chrysalides  of 

Tenebrio  molitor  at  different  temperatures.     Zeits.  allgem.  Phys.,  bd.   i6,  pp. 

178-190,  figs.  1-3. 
Parks,  T.  H.     1914.     Effect  of  Temperature  upon  the  Oviposition  of  the  Alfalfa  Weevil 

(Phytonomus  posticus  Gyllenhal).     Journ.  Econ.  Ent.,  vol.  7,  pp.  417-421,  3  figs. 
Peairs,L.  M.     1914.     The  Relation  of  Temperature  to  Insect  Development.     Journ.  Econ. 

Ent.,  vol.  7,  pp.  174-179,  figs.  10-15. 
Shelford,  V.  E.     1914.     The  Importance  of  the  Measure  of  Evaporation  in  Economic 

Studies  of  Insects.     Journ.  Econ.  Ent.,  vol.  7,  pp.  229-233. 
Shelford,  V.  E.     1914.     An  Experimental  Study  of  the  Behavior  Agreement  among  the 

Animals  of  an  Animal  Community.     Biol.  Bull.,  vol.  26,  pp.  294-315,  figs.  1-41.* 
Vestal   A.  G.     1914.     Internal  Relations  of  Terrestrial  Associations.     Amer.  Nat.,  vol. 

48,  pp.  413-445- 
Weiss,  H.  B.     1914.     Thermal  Conductivity  of  Cocoons.     Psyche,  vol.  21,  pp.  45-5°- 
Bishopp,  F.  C,  Dove,  W.  E.,  and  Parman,  D.  C.     1915.     Notes  on  Certain  Points  of  Eco- 
nomic Importance  in  the  Biology  of  the  House  Fly.     Journ.  Econ.  Ent.,  vol. 

8,  pp.  54-71- 
Bueno,  J.  R.  de  la  T.     1916.     Aquatic  Hemiptera.     A  Study  in  the  Relation  of  Structure 

to  Environment.     Ann.  Ent.  Soc.  Amer.,  vol.  9,  pp.  353-365. 
Rau,  P.  and  N.     1916.     The  Sleep  of  Insects;     an  Ecological  Study.     Ann.  Ent.  Soc. 

Amer.,  vol.  9,  pp.  227-274.* 
Baumberger,  J.  P.     1917.     Hibernation:  a   Periodical   Phenomenon.     Ann.    Ent.    Soc. 

Amer.,  vol.  10,  pp.  179-186.* 
Elwyn,  A.     1917.     Effect  of  Humidity  on  Pupal  Duration  and  on  Pupal  Mortality  of 

Drosophila  ampelophila Loew.     Bull.  Amer.  Mus.  Nat.  Hist,  vol.  37,  pp.  347^353- 
Headlee,  T.  J.     1917.     Some  Facts  Relative  to  the  Influence  of  Atmospheric  Humidity  on 

Insect  Metabolism.     Journ.  Econ.  Ent.,  vol.  10,  pp.  31-38. 


476  ENTOMOLOGY 

Loeb,  J.,  and  Northrop,  J.  H.     1917.     On  the  Influence  of  Food  and  Temperature  upon  the 

Duration  of  Life.     Journ.  Biol.  Chem.,  vol.  32,  pp.  103-121. 
Tillyat'd,  R.  J.     1917.     The  Biology  of  Dragonflies.     12  +  396  pp.,  188  figs.     Cambridge. 

University  Press. 
Ely,  C.  R.     1918.     Recent  Entomological  Chemistry  and  Some  Notes  concerning  the 

Food  of  Insects.     Proc.  Ent.  Soc.  Washington,  vol.  20,  pp.  "12-18. 
Headlee,  T.  J.     1918.     Climate  and  Insect  Investigations.     Rept.  Dept.  Ent.,  N.  J.  Agr. 

E.xp.  Sta.,  191 7,  pp.  442-445- 
Shelford,   V.  E.     1918.     Physiological  Problems  in  the  Life-Histories  of  Animals  with 

Particular  Reference  to  their  Seasonal  Appearance.     Amer.  Nat.,  vol.  52,  pp.  129- 

154.* 
Baumberger,  J.  P.     1919.     A  nutritional  study  of  insects  with  special  reference  to  micro- 
organisms and  their  substrata.     Journ.  Exp.  Zool.,  vol.  28,  pp.  1-81,  18  figs.* 
Riley,  C.  F.  C.     1919.     Some  Habitat  Responses  of  the  Large  Water-Strider,  Gerris 

remigis  Say.     Amer.  Nat.  vol.  53,  pp.  394-414;  483-505. 
Brues,  C.  T.     1920,     The  Selection  of  Food-Plants  by  Insects,  with  Special  Reference  to 

Lepidopterous  Larvae.     Amer.  Nat,  vol.  54,  pp.  313-332. 
Dozier,  H.  L.     1920.     An  Ecological  Study  of  Hammock  and  Piney  Woods  Insects  in 

Florida.     Ann.  Ent.  Soc.  Amer.,  vol.  13,  pp.  325-380,  22  figs.* 
Pannan,  D.  C.     1920.     Observations  on  the  Effect  of  Storm  Phenomena  on  Insect  Activity. 

Journ.  Econ.  Ent.,  vol.  13,  pp.  339-343- 
Peterson,  A.     1920.     Some  Studies  on  the  Influence  of  Environmental  Factors  on  the 

Hatching  of  the  Eggs  of  Aphis  avenae  Fabricius  and  Aphis  pomi  DeGeer.     Ann. 

Ent.  Soc.  Amer.,  vol.  13,  pp.  391-400,  pi.  31.* 
Riley,  C.  F.  C.     1919.     Some  Habitat  Responses  of  the  Large  Water-Strider,   Gerris 

remigis  Say.     Amer.  Nat.,  vol.  52,  pp.  394-631,  figs.  1-6.* 
Riley,  C.  F.  C.     1920.     Migratory  Responses  of  Water-Striders  during  Severe  Droughts. 

Bull.  Brooklyn  Ent.  Soc,  vol.  15,  pp.  i-io. 
Claassen,  P.  W.     1921.     Typha  Insects:  Their  Ecological  Relationships.     Cornell  Univ. 

Agr.  Exp.  Sta.,  Memoir  47,  pp.  459-529,  pis.  39-48.* 
Craighead,  F.  C.     1921.     Hopkins  Host-Selection  Principle  as  Related  to  Certain  Ceram- 

bjxid  Beetles.     Journ.  Agr.  Res.,  vol.  22,  pp.  189-220. 
Headlee,  T.  J.     1921.     The  Response  of  the  Bean  Weevil  to  Different  Percentages  of 

Atmospheric  Moisture.     Journ.  Econ.  Ent,  vol.  14,  pp.  264-268,  fig.  5. 
Livingston,  B.  E.,  and  Shreve,  F.     1921.     The  Distribution  of  Vegetation  in  the  United 

States,  as  Related  to  Climatic  Conditions.     Carnegie  Inst.  Washington,  Pub. 

No.  284,  16  +  590  pp.^  74  figs.,  73  pis.* 
Ping,  C.     1921.     The  Biology  of  Ephydra  subopaca  Loew.     Cornell  Univ.  Agr.  Exp.  Sta., 

Memoir  49,  pp.  557-616,  pis.  54-S7-* 
Riley,   C.  F.  C.     1921.     Distribution  of  the  Large  Water-Strider,   Gerris  remigis  Say, 

throughout  a  River  System.     Ecology,  vol.  2,  pp.  32-36,  figs.  1-3. 

INSECTS  IN  RELATION  TO  MAN 

Harris,  T.  W.     1862.     A  Treatise  on  Some  of  the  Insects  Injurious  to  Vegetation.     Third 

Ed.     II  -f  640  pp.,  278  figs.,  8  pis.     Boston. 
Lintner,  J.  A.     1882.     Importance  of  Entomological  Study,  etc.     First  Ann.  Rept.  Inj. 

Ins.,  pp.  1-80,  figs.  1-12. 
Saunders,  W.     1883.     Insects  Injurious  to  Fruits.     436  pp.,  440  figs.    Philadelphia.    J.  B. 

Lippincott  &  Co. 
Packard,  A.  S.     1889.     Guide  to  the  Study  of  Insects.     Ed.  9.     12  +  715  pp.,  668  figs., 

15  pis.     New  York.     Henry  Holt  &  Co. 


LITERATURE  477 

Howard,  L.  O.     1894.     A  Brief  Account  of  the  Rise  and  Present  Condition  of  Official  Eco- 
nomic Entomology.     Insect  Life,  vol.  7,  pp.  55-107. 
Sempers,  F.  W.     1894.     Injurious  Insects  and  the  Use  of  Insecticides.     10  +  216  pp.,  i  pi., 

184  fijis.     Philadelphia.     W.  A.  Burpee  &  Co. 
Smith,  J.  B.     1896.     Economic  Entomology  for  the  Farmer  and  Fruit-Grower,  etc.     Pp 

12  +  1 1-48 1,  483  figs.     Philadelphia.     J.  B.  Lippincott  Co. 
Howard,  L.  O.     1899.     The  Economic  Status  of  Insects  as  a  Class.     Science,  vol.  9  (n.  s.) 

pp.  233-247. 
Theobald,  F.  V.     1899.     A  Text-Book  of  Agricultural  Zoology.     17  +  511  pp.,  225  figs 

Edinburgh  and  London.     Wm.  Blackwood  &  Sons. 
Howard,  L.  O.     1900.     Progress  in  Economic  Entomology  in  the  United  States.     Yearbook 

U.  S.  Dept.  Agric,  1899,  pp.  135-156,  pi.  3- 
Sanderson,  E.  D.     3902.     Insects  Injurious  to  Staple  Crops.     10  +  295  pp.,   163  figs 

New  York.     John  Wiley  &  Sons. 
Lodeman,  E.  G.     1903.     The  Spraying  of  Plants.     17  +  399  pp.,  92  figs.     New  York 

The  Macmillan  Co.* 
Chittenden,   F.  H.     1907.     Insects  Injurious  to   Vegetables.     14  -f  262   pp.,    163   figs, 

New  York.     Orange  Judd  Co.* 
Johnson,    W.    G.     1908.     Fumigation    Methods.     16  +  313    pp.,    83    figs.    New  York 

Orange  Judd  Co. 
Smith,  J.  B.     1909.     Our  Insect  Friends  and  Enemies.     314  pp.,  121  figs.     Philadelphia. 

J.  B.  Lippincott  Co. 
O'Kane,  W.  C.     1912.     Injurious  Insects;  How  to  Recognize  and  Control  Them.     11  + 

414  pp.,  606  figs.     New  York.     Macmillan  Co. 
Sanderson,  E.  D.     1912.     Insect  Pests  of  Farm,  Garden  and  Orchard.     12  +  684  pp.,  513 

figs.     New  York.     John  Wiley  &  Sons. 
Bourcart,  E.     1913.     Insecticides,  Fungicides  and  Weed  Killers.     Trans,  by  D.  Grant. 

35  +  431   pp.     London.   Scott,   Greenwood  &   Son.     New  York.   D.  Van  Nost- 

rand  Co. 
Herrick,  G.  W.     1914.     Insects  Injurious  to  the  Household  and  Annoying  to  Man.     17  + 

470  pp.,  152  figs.,  8  pis.     New  York.  -   The  Macmillan  Co.* 
Imms,  A.  D.     1914.     The  Scope  and  Aims  of  Applied  Entomology.     Parasitology,  vol.  7, 

pp.  69-87.* 
Slingerland,  M.  V.,  and  Crosby,  C.  R.    1914.     Manual  of  Fruit  Insects.     16  +  503  pp., 

396  figs.     New  York.     The  Macmillan  Co.* 
Hewitt,  C.  G.     1916.     A  Review  of  Applied  Entomology  in  the  British  Empire.     Ann.  Ent. 

Soc.  Amer.,  vol.  9,  pp.  1-34. 
Osbom,  H.     1916.     Agricultural  Entomology.      Pp.  4  +  17-347,  252  figs.     Philadelphia 

and  New  York.     Lea  &  Febiger. 
Crosby,  C.  R.,  and  Leonard,  M.  D.     1918.     Manual  of  Vegetable-Garden  Insects.     15  + 

391  pp.,  232  figs.     New  York.     The  Macmillan  Co.* 
Lochhead,  W.     1919.     Classbook  of  Economic  Entomology.     14  -|-  436  pp.,   257  figs. 

_  Philadelphia.     P.  Blakiston's  Son  &  Co.* 
Femald,    H.    T.     1921.     Applied   Entomology.     14  +  386    pp.,    388    figs.     New  York. 

McGraw-Hill  Book  Co.,  Inc. 
Sanderson,  E.  D.,  and  Peairs,  L.  M.     1921.     Insect  Pests  of  Farm,  Garden  and  Orchard. 

Ed.  2.  6  +  707  pp.,  604  figs.  New  York.  John  Wiley  &  Sons,  Inc. 
Most  of  the  literature  on  the  economic  entomology  of  the  United  States  is  contained  in 
the  following  works:  Reports  U.  S.  Ent.  Commission;  Repts.  Govt.  Entomologists;  Bulletins 
U.  S.  Dept.  Agric,  Bur.  Ent.;  Bull.  U.  S.  Dept.  Agric;  Journ.  Agric.  Research,  U.  S. 
Dept.  Agric;  Insect  Life;  Reports  and  Bulletins  by  the  several  State  Entomologists; 
Bulletins  of  the  various  Experiment  Stations;  Journal  of  Economic  Entomology. 


INDEX 


An  asterisk  *  denotes  an  illustration. 


Abbott,  461 

Abdomen,   60;   appendages  of,    *6i,    *i32, 

*i33;  extremity,  62;  modifications,  61; 

segments,  60 
Acacia,  *2so 

Accessory  glands,  *i24,  125 
Acclimatization,  360 
Acerentomon,  *6 
A  chortiles,'^*  10 
Acone,  98 

Acridiidae  (see  Locustida). 
Aculeata,  19 
Adams,  339,  472,  475 
Adaptations,  of  larvae,  145;  of  legs,  48,  *5o; 

of  mandibles,  *36;  protective,  245 
Adaptive  coloration,  194;  classification,  210; 

evolution,  211 
Adelung,  von,  444 
Adier,  439,  462 
Adventitia,  no 
Adventitious  resemblance,  197 
Aedes,  255,  269 
^geria,  sexual  coloration,  184 
-Estivation,  366 
Ageronia,  92 

Aggressive  resemblance,  210 
Agrionidae,  caudal  gills,  *ii9 
Air,  movement,  368;  of  soil,  350;  of  water, 

383 
Air-sacs,  117 
Alary  muscles,  *io9 
.\lbinism,  179 
Aldrich,  384,  414,  426 
Alexander,  460 

Alimentary  tract  (see  Digestive  system) . 
Allard,  445 

Alluring  coloration,  210 
Alternation  of  generations,  216 
Amans,  437,  455 
Amber  insects,  341,  345 
Ametabola,  140 
Ammophila,  *3i7 
Amnion,  *i3i,  135 
Amphidasis,  178 


Amphigony,  358 

Amphipyra,  304 

Ampullaceum,  *85 

Anajapyx,  *6,  21 

Anal  glands,  73,  *io3 

Anasa,  *i38 

Anderson,  269 

Androconia,  *7i,  72 

Anemotropism,  305 

Aner gates,  294 

AngrcBcuni,  221 

Anisota,  *i52 

Anisotropic,  78 

Annelids,  in  relation  to  arthropods,  5,  *8 

Anomma,  293 

Anopheles,  250,  251 

Anophthalmus,  100 

Anosia  berenice,  337;  plexippus,  antenna  of, 
*32;  dispersal,  325;  eclosion,  152; 
so-called  mandibles,  40;  mimicry,  *20i, 
207;  pupa,  *i47;  pupation,  147;  scale, 
*7o;  wing,  *55 

Anteclypeus,  29 

Antecoxal  piece,  *47 

Antennae,  forms  of,  *32;  functions,  ^:^;  sex- 
ual differences,  *3S 

Antennal  comb,  *2  28,  229;  neuromere,  *43; 
segment,  44;  sensilla,  84,  *85 

Anthononius  grandis,  activity,  353;  aestiva- 
tion, 366;  coloration,  378;  develop- 
ment, SS5,  359,  360;  fecundity,  376; 
food,  376;  hibernation,  361;  longevity, 
377;  rainfall  on,  366;  spread  in  U.  S., 
418;  winds  on,  368 

Anthrax,  269 

Anthrenus,  *6g 

Antigeny,  34,  *i84 

Ant-plants,  *23o 

Ants,  castes  of,  289;  color  sense,  100;  facets, 
31;  general  account,  289;  habits,  291; 
harvesting  ants,  297,  400;  honey  ants, 
*294;  hunting  ants,  293;  larvae,  290; 
leaf-cutting,  *295;  nests,  290;  photo- 
tropism,  310;  slavemaking,  293 


48o 


INDEX 


Anurida,  development  of  mouth  parts, 
*i32;  germ  band,  *i32;  habits,  170; 
pigment,  177 

Anus,  *66,  105 

Aorta,  *io9 

Apanteles,  *2  73 

Apatetic  colors,  210 

A  pat  lira,  scales,  172;  colors,  175 

Aphididas,  development,  359;  galls  of,  * 2 14; 
reproduction,  358 

Aphidius,  273 

Apis  mellifera,  antennal  sensilla,  *85;  ce- 
phalic glands,  107;  comb,  282,  *283; 
control  of  sex,  286;  determination  of 
caste,  286;  foot,  *5i;  general  account, 
281;  hair,  *227;  larvae,  *284;legs,  *228; 
mandible,  *36;  mimicry,  *202;  modi- 
fications in  relation  to  flowers,  *228; 
mouth  parts,  *42;  ocellus,  *96;  oviposi- 
tor, *64;  pupa,  *284;  reproductive  sys- 
tem, *i26;  tongue,  *86;  wax,  *74,  282 

Apneustic,  117,  169 

Apodemes,  *48 

Apodous  larvae,  44,  5 1 

Apophyses,  *48 

A  poms,  319 

Appendages,  development  of,  *i3i 

Apple,  insects  of,  212,  410 

Aptera,  7 

Apterygota,  9 

Aquatic  insects,  adaptations  of,  165;  condi- 
tions of  existence,  382;  food,  165,* 386; 
locomotion,  166;  origin,  171;  respira- 
tion, 168;  systematic  position,  165 

Arachnida,  *2 

Arctic  realm,  331 

Arista,  *32 

Aristida,  297 

Arixeniidae,  10 

Arms,  J.  M.,  21,  431,  432,  454 

Army  worm,  339 

Arthropoda,  characters  of,  *i;  classes,  2; 
interrelationships,  4;  naturalness  of 
phylum,  7;  phylogeny,  *8 

Asclepias,  221,  *222,  *223 

Asecodes,  274 
Ashmead,  327 
Aspidiotus    perniciosits,    spread    of,    418; 

\vinter-killing  of,  363 
Assembling,  90 
Associations,  393,  394 
Ast,  446 


Atelnra,  *300 

Atemeles,  *299 

Atmosphere,    351;    composition    of,    367; 

movement,  368^  temperature,  352 
Atta,  293,  *295 
Attactis,  27 

Auditory  hairs,  94;  organs,  94,  *9S 
Aughey,  on  insectivorous  birds,  243,  463 
Auricle,  *228,  229 
Austen,  465 
Australian  realm,  332 
Austral  region,  332 
Autecology,  348 
AiUomeris,  73 
Ayers,  61,  452 

Bachmetjew,  364 

Back,  E.  A.,  429 

Backswimmers  (see  Notonecta). 

Baldwin,  469 

Ball,  E.  D.,  426 

Ballowitz,  450 

Banks,  430,  434 

Barber,  384,  456 

Barriers,  324 

Barrows,  303,  470 

Basement  membrane,  *67,  69,  *io5 

Basiconicum,  84,  *85 

Basidium,  *2i8 

Basilarchia,  mimicry,  *2oi,  207;  protective 

resemblance,  196 
Bates,  on  mimicry,  202,  459,  470,  471 
Batesian  mimicry,  203 
Bateson,  458 
Bauer,  442- 

Baumberger,  354,  361,  373,  374,  475,  476 
Beal,  240,  463 
Bean  weevil  (see  Bruchus). 
Beddard,  457,  460,  472 
Bees,  color  sense  of,  100;  hairs,  *68 
Beetles,  sounds  of,  91 
Behavior  of  insects,  302 
Bellesme,  de,  446 
Belostoma,  digestive  system  of,  ^105;  pre- 

daceous,  166,  233 
Belt,  on  leaf-cutting  ants,  295,  471 
Bembidion,  303,  349 
Benacus,    *i5;  caecum,   105;  mouth  parts, 

*39;  predaceous,  166 
Beneden,  van,  466 
Beneficial  insects,  41 1 
Benton,  oh  honey  bee,  286,  466 


INDEX 


481 


Berlese,  160,  431,  433 

Bernard,  432 

Bertkau,  126 

Bethe,  292,  469 

Bethune,  429 

Betten,  456 

Binet,  442 

Biotic  conditions,  379,  387 

Birches,  insects  of,  212 

Bird,  H.,  349 

Birds,  insectivorous,  239;  regulating  insect 

oscillations,  243 
Bishopp,  352,  365,  475 
Bittacomorpha,  *i20,  169 
Biltactis,  *i6,  *49 
Bitter  rot,  219 
Black-flies,  233 
Blackiston,  460 
Blanc,  436,  447 
Blanchard,  464 
Blandford,  464 
Blastoderm,  *i3o 
Blastophaga,  428 
Blatchley,  426 

Blalla,  muscles  of,  *77;  respiration,  *i2i 
Blattidje,  10 
Blind  insects,  2,3 
Blissus    leiicopterusy    distribution    of,    339; 

drought    on,     366;    incubation,     359; 

losses  through,  410;  rainfall  on,  367 
Blochmann,  452 
Blood,    corpuscles,    *iio;    course   of,    no, 

*iii;  function,  in;  gills,  119 
Bluebird,  food  of,  241 
Blunck,  453 
Boas,  455 
Bobretzky,  452 
Boll  weevil  (see  Anlhonomus). 
Boll  worm  (see  Chloridea). 
Bolton,  430 
Bombiis,  antenna  of,  *32;  general  account, 

287;  larva,  *i42;  mimicry,  *2io;  respi- 
ration, *i2i;  taste  cup,  *88 
Bombyx  mori,  Malpighian  tubes  of,  *io8; 

mid  intestine,   *io5;  cenocytes,   *n4; 

silk  glands,  *76 
Bordas,  441,  447 
Boreal  region,  332 
Borgert,  441 
Borner,  433,  434 
Bot  flies,  234 
Bourcart,  477 
31 


Bouvier,  433,  470 

Boyce,  465 

Brachiniis,  73 

Brachj'pterism,  397 

Braconidas,  273 

Brain,  80,  *82;  functions  of,  82 

Branchial  respiration,  169 

Brandt,  451 

Brauer,  on  classification,  7;  types  of  larvae, 

142)432,  453 
Br  aula.  272 
Braun,  464,  465 
Breed,  on  phagocytosis,  160 
Breithaupt,  436 
Bridges,  461 
Britton,  425 
Brongniart,  on  Carboniferous  insects,  341, 

344,.473 
Brown-tail  moth  (see  Euproctis). 
Bruce,  263,  264,  465 
Bruchophagiis,  *I39 
Bruchus,  metabolism,  364,  370 
Brues,  269,  359,  366,  372,  374,  434,  465,  467, 

476 
Bruner,  426 

Brunner  von  Wattenwyl,  458 
Bruntz,  448 
Buckingham,  470 
Bugnion,  162,  454 
Bumblebees,  general  account,  287 
Bureau  of  Entomology,  428 
Burge,  lis 
Burger,  370 

Burgess,  A.  F.,  368,  429 
Burgess,  E.,  436 
Burmeister,  431,  432 
Bursa  copulatrix,  125 
Busck,  139 
Biithus,  *2 
Butler,  459 

Biitschli,  442,  450,  451,  452 
Butterflies,   eclosion  of,    152,    *i53;   fossil, 

*346 

Cabbage  butterfly  (see  Pier  is  rapa). 

Caeca,  gastric,  *io2,  *io3,  104 

Cacilius,  *io6 

Cascum,  *io4,  *io5 

Caesar,  445 

Cajal,  449 

Calkings,  465 

CaUiphora,  compound  eyes  of,  *97,  *98 


482 


INDEX 


Callosamia,  antennae,   2>y':  assembling,   90; 

cocoon,  356;  sexual  coloration,  *i85 
Caloptenus,  olfactory  organ  of,  *88;  tym- 
panal organ,  *95 
Calopteryx,   development  of,    *i34;   sexual 

coloration,  185 
Calvert,  465 
Cameron,  475 

Campodea,  6,  *g,  21,  60,  *i42 
Candeze,  440 

Canker  worms,  as  food  of  birds,  243 
Cannon,  307 
Canthon,  *5o 
Capitate,  *32 
Carabids,  anal  glands  of,  73,  *io3;  food  of, 

233;  predaceous,  271 
Carabidoid  larva,  *i57 
Carahus,  alimentary  tract  of,  *io3 
Carboniferous  insects,  341,  342 
Cardiac  valve,  *ioi,  102,  *io4 
Cardo,  *37 
Carle  t,  439 

Carpenter,  F.  W.,  469 
Carpenter,  G.  H.,  5,  7,  43I)  433,  455,  45^, 

461,  472 
Carpocapsa  pomonclla,   development,   356, 
360;  hibernation,  361;  incubation,  358; 
temperature  on,  356;  winter-killing  of, 
362 
Carriere,  444,  452 
Carrion  insects,  236 
Carroll,  253,  255,  465 
Cams,  430 
Casteel,  229,  463 
Catbird,  foot  of,  240 
Caterpillar,  137;  pupation  of,  147,  *i49 
Catocala,    protective    resemblance,     *i9s; 

scent  tufts,  49 
Caiogenus,  antenna  of,  *32 
Caudal  gills,  170 
Caudell,  434,  435 
Cecidomyiidie  (see  Itonidida). 
Cecropia  adettopus,  230,  *23i,  *232 
Cecropia  moth  (see  Samia). 
Centipede,  *5 
Centrolecithal,  *i30 
Cerambyx,  facets  of,  31;  ovipositor,  *63 
Ceralina,  277 
Ceratomegilla,  336 
Cerceris,  319 
Cerci,  *g,  62,  *6s,  *6s 
Cercopoda,  62 


Ceroplaslcs,  75 

Cerura,  74 

Cervical  sclerites.  29 

Chadwick,  463 

Chajticum,  84,  *85 

Chalcididae,  27,  273 

Chandler,  465 

Chapman,  453 

Chelostoma,  *68 

Chemotropism,  302 

Cheshire,  42,  64,  229,  283 

Child,  444 

Chilopoda,  3,  *5 

Chinch  bug  (see  Blissiis). 

Chionaspis,  141 

Chironomus,   nervous  system,    *82;    pupal 

eggs,  128 
Chitin,  66 

Chittenden,  429,  474,  477 
Chloridea  obsoleta,  development,  359;   rain- 
fall on, 366 
Chlorophyll,  as  a  pigment,  175 
Cholera,  268 

Cholodkovsky,  432,  447,  452 
Chordotonal  organs,  *95 
Chorion,  *i29,  141 
Christophers,  465 
Christy,  464 
Chro  mosomes,  1 2  9 
Chrysalis,  137 
Chrysobothris,  integument  of,  *67 

Chrysomelidae,  silk  glands  of,  77 
Chrysopa,  *i6;  cocoon  of,  *i48;  laying  eggs, 
*i4o;  mandibles,  *36;  predaceous,  270; 
silk  glands,  77 

Chun,  440 

Cicada,  metamorphosis  of,  *i39;  molts,  145; 
sound,  91 

Cicindela,  leg  of,  *5o;  mandible,  *s6;  pre- 
daceous, 271;  variation  in  coloration, 
183,  189,  *I92 

Cicindelidae,  ecological  succession  of,  407; 
eggs,  350,  351 

Cimbex,  repellent  glands,  73 

Circular  muscles,  *io5,  106 

Circulation,  *iii 

Circulatory  system,  109 

Cirphis  unipuncta,  339 

Claassen,  476 

Claspers,  *65,  *66 

Claus,  432 

Clavate,  *32 


INDEX 


483 


Claypole,  453 

Clements,  474 

Climatal  coloration,  179 

Clisodon,  225 

Cloaca,  62 

Clover,  insects  of,  212,  410;  pollination  of, 
225 

Clypeus,  28,  *4o 

Clylra,  embryology  of,  *i30,  *i3i,  *i3S, 
*i36 

Cnemidotus,  118 

Coarctate  pupa,  147 

Coblentz,  116,  449 

Coccinella,  distribution  of,  336 

Coccinellidc-E,  predaceous,  271;  silkglands,  77 

Cochineal,  413 

Cockerell,  347,  426 

Cockroach,  cephalic  ganglia  of,  *82;  fossil, 
*343j  345;  mouth  parts,  *35;  muscles, 
*53>  *77;  respiration,  *i2i;  salivafy 
gland,  *io7;  spermatozoon,  *i25 

Cocoon,  *i48,  *isi 

Codling  moth  (see  Carpocapsa). 

Cceloconicum,  84,  *85 

Ccelom  sacs,  "135 

Coleoptera,  16,  *i5,  24 

Colias,  albinism  of,  180;  color  sense,  100; 
sexual  coloration,  *i84 

Collembola,  alimentary  tract  of,  *ioi;  de- 
fined, 9;  furcula,  62;  primitive  condi- 
tion, 21;  ventral  tube,  62 

Colletes,  hairs  of,  *68 

Colon,  *io2,  105 

Colopha,  gall  of,  *2i4 

Coloradia,  414 

Color,  effects  of  food  on,  176;  sources  of,  172 

Colorado  potato  beetle  (see  Leptinotarsa). 

Coloration,  adaptive,  194,  210;  climatal, 
179;  development  of,  187;  effects  of 
moisture  and  temperature  on,  178; 
seasonal,  180;  sexual,  184;  variation  in, 
188;  warning,  199 

Color  patterns,  development  of,  187;  ori- 
gin,   186 

Colors,  combination,  175;  pigmental,  174; 
structural,  172 

Color  sense,  100 

Commissures,  80,  *82 

Communities,  393;  classification  of,  389, 
393;  distribution  of,  389;  examples  of, 
394;  grasshopper,  394;  stream,  397;  in 
New  Mexico,  399 


Complete  metamorphosis,  137 

Compound  eyes,  *25;  origin,  100;  physiol- 
ogy) 98;  structure,  *97,  *98 

Comstock,  A.  B.,  128,  290 

Comstock,  J.  H.,  56,  424,  427,  431,  432,  433, 
434,  435,  436,  438,  455,  45^ 

Comte,  267 

Cone  cells,  97,  *98 

Conidia,  *2i8 

Conidiophores,  *2i8 

Connold,  462 

Conradi,  426 

Conseil,  267 

Consocies,  393 

Cook,  A.  J.,  426 

Cook,  M.  T.,  462 

Cooke,  462 

Cooley,  426 

Cooties  (see  Pediculus). 

Cope,  on  segmentation,  27 

Copidosoma,  273,  412 

Copris,  spermatozoon  of,  *i25 

Coprophaga,  373 

Coquillett,  424 

Corbiculum,  *228 

Cordley,  426 

Cordyceps,  *2i7 

Corethra,  chordotonal  organs  of,  *95;  imag- 
inal  buds,  *i6i 

Corn  borer  (see  Pyrausta). 

Corn  ear  worm  (see  Chloridea). 

Corn  insects,  212,  410 

Cornea,  *97,  *98 

Corrodentia,  *i2 

Corydaloides,  344 

Cosens,  215,  463 

Costa,  *54 

Coste,  457 

Cotton  boll  weevil  (see  Anthonomus) . 

Cotton  boll  worm  (see  Chloridea). 

Cotton  worm,  410 

Cowan,  462 

Coxa,  48 

Craig,  465 

Craighead,  476 

Crampton,  21,  23,  25, 434, 435, 437, 438,.  440 

Crawley,  467 

Cremaster,  147 

Cremastogaster,  291 

Cricket,  stridulation  of,  93 

Crioceris,  338 

Crop,  *i02,  *io3 


484 


Crosby,  424,  477 

Crustacea,  2 

Cryptorhynchus,  338 

Crystalline  cone,  97,  *98 

Ctenocephalus,  *20 

Cubitus,  *54 

Cucurbit  wilt,  219 

Cuenot,  441,  447,  448 

Ciilex,  antennae  of,  *34;  characteristics,  251; 
filariasis  transmitted  by,  265;  hiberna- 
tion, 310;  larva,  *i68;  mouth  parts, 
*4i;  respiration,  169;  tropisms,  310 

Cutaneous  respiration,  169 

Cuticula,  66,  *67,  *68 

Cuticular  colors,  1 74 

Cyaniris  pseudargiolus,  coloration  of,  178; 
geographical  varieties,  328;  melanism, 
180;  polymorphism,  *i8i;  sexual  color- 
ation, 184 

Cybister,  leg  of,  *i67;  locomotion,  167,  168 

Cychrits,  91 

Cyllene,  metamorphosis  of,  *i37 

Cynipidse,  abdomen  of,  61;  galls,  *2i3, 
*2i4;  parthenogenesis,  127,  216 

Cyrtophyllus,  stridulation  of,  93 

Dahl,  437,  440,  442 

Darkness,  as  affecting  pigmentation,  177 

Darts,  *64 

Darwin,  317,  412,  461,  462,  470 

Dasyneura,  egg  of,  *i39, 140;  ovipositor,  *63 

Davenport,  308,  352,  353,  360,  364,  469,  474 

Davis,  J.  J.,  426 

Davis,  K.  C,  456 

Dean,  425 

Dearborn,  on  insectivorous  birds,  242,  243, 

245,  464 
Deegener,  441,  442,  443,  445,  447,  448,  450, 

45i>  455 
Demoll,  437,  445,  446 
Demoor,  437 

Denny,  66,  78,  431,  435,  442 
Dermaptera,  10 
Dermestidae,  236 
Deutocerebrum,  80,  135 
Deutoplasm,  *i29 
Development,  129 
Development,  threshold  of,  355 
Developmental  zero,  355 
Devonian  insects,  340,  341 
Dewar,  461 
Dewitz,  437,  439,  448,  454 


Diabrotica,  distribution  of,  337 

Diacrisia,  cocoon  of,  148 

Diapheromera,  195,  359 

Diastole,  in 

Dibrachys,  274 

Dichoptic,  *32 

Dickel,  467 

Dictyoneiira,  344 

Dietrich,  445 

Digestive  system,  loi;  of  beetle,  *ioy, 
Belosloma,  *io5;  Collembola,  *ioi; 
grasshopper,  *io2;  histology,  *io5; 
106;  moth,  *io4;  Myrmeleon,  *io3 

Digoneutic,  182 

Dimmock,  on  assembling,  91;  on  mouth 
parts  of  mosquito,  *4i;  436,  440,  457, 
463 

Dimorphism,  180 

Dinar  da,  *2gg 

Dineutus,  antenna  of,  *32;  eyes,  *30 

Diplopoda,  *3 

Diptera,  19,  *2o;  eyes  of,  *3i;  halteres,  loi; 
mouth  parts,  *4i;  origin,  25;  sounds, 
91;  spiracles,  60 

Direct  metamorphosis,  138 

Directing  tube,  76 

Diseases,  their  transmission  by  insects,  218, 
248 

Dispersal,  322;  centers  of,  339;  means  of, 
323;  in  North  America,  335 

Dissosteira,  protective  resemblance  of,  196; 
stridulation,  92 

Distant,  471 

Distribution,  former  highways  of,  325;  geo- 
graphical, 322;  geological,  340;  tem- 
perature on,  362 

Diving  beetles  (see  DytiscidcB). 

Dixey,  208,  457,  458,  460 

Doane,  465 

Dogiel,  447 

Dolbear,  on  stridulation,  93 

Dolichopodidae,  49 

Dolley,  470 

Donacia,  79,  165,  169 

Doncaster,  451 

Donisthorpe,  467 

Dorfmeister,  457 

Dorsal  vessel,  *io9,  *iio 

Doten,  376,  426,  474 

Dove,  352,  365,  475 

Dozier,  476 

Drift,  insect,  1 70 


INDEX 


485 


Drone,  *282 
Drosera,  216 
Drosophila,    chemotropism    of,    303;    egg, 

♦139;  food,  373,  376;  humidity  on,  365; 

melanism,  180;  phototropism,  310,  311 
Drought,  366 
Dubois,  448 

Ductus  ejaculatorius,  *i24 
Dufour,  449,  455 
Durham,  464 
Diirken,  438 
Dyar,  on  molts,  145 
Dynastes  hercules,  27;  tityiis,  distribution  of, 

337 
Dysentery,  268 
Dytiscidae,  166,  167 
Dytiscus,  caecum  of,  105;  leg  of,   *5o;  pre- 

daceous,  233;  respiration,  169 
Dzierzon's  theory,  286 

Ecdysis,  140,  144 

Ecilon,  *295;  eyes  of,  31;  habits,  233,  290,293 

Eckstein,  462 

Eclosion,  152 

Ecology,  348 

Economic  entomologist,  420 

Ectoderm,  130,  *i3i 

Edwards,  on  /.  ajax,  182;  on  P.  tharos,  182 

Effective  temperatures,  355 

Egg-guide,  *67 

Egg-nucleus,  *i29 

Eggs,  form  of,  *i39;  number,  141;  size,  140 

Eimer,  468 

Ejaculatory  duct,  *i24 

Elaplirus,  stridulation  of,  91 

Electricity,  368 

Eleodinae,  372 

Ellema,  protective  resemblance  of,  196 

Elm,  insects  of,  212 

Elm  leaf  beetle  (see  GaleruccUa). 

Eltringham,  446,  461 

Elwes,  471 

Elwyn,  365,  475 

Ely,  476 

Elytra,  53 

Enihia,  12 

Embioptera,  ix 

Embryology,  129 

Emery,  448,  467 

Emcsa,  322 

Empis,  nervous  system  of,  *82 

Empodium,  48 


Emptisa,  *2i8 

Enderlein,  433 

Endoskeleton,  46,  *48 

Engelmann,  430 

Enteman,  289,  321,  459,  467,  469 

Entoderm,  130,  135,  *i36 

Entomophagous,  373 

Entomophthoracea;,  217,  *2i8 

Environment,  387,  389 

Ephemerida,  *i3,  14;  abdominal  segments 
of,  60;  eyes,  31;  origin,  23 

Ephydra,  383,  414 

£/)/f aw/a,  hypermetamorphosis  of,  156,  *i57 

Epicranium,  28 

Epigamic  colors,  211 

Epimeron,  *45,  *47 

Epipharynx,  35 

Episternum,  *45,  *47 

Epitheca,  dorsal  vessel  of,  *iio 

Equilibrium,  382 

Erebus  agrippina,  27;  odora,  323,  337 

Ergatoid,  290 

Eriocepliala,  mouth  parts  of,  40 

Eristalis,  mimicry  by,  *202;  respiration,  169 

Eruciform  larvae,  24,  *i43,  160 

Erynnis  manitoba,  distribution  of,  *332 

Escherich,  439,  451 

Essig,  425 

Ethiopian  realm,  331 

Etiolin,  193 

Etoblattina,  343 

Eucone,  98 

Eitdamus  proteus,  distribution  of,  *332 

Eiigercon,  *344 

Euphoria,  mouth  parts  of,  36,  *2  2  7 

Euplexoptera  (see  Dermaptera). 

Euplcea,  colors  of,  175 

Euproctis  chrysorrhoea,  phototropism  of, 
309;  spread,  417;  winter-killing  of,  362 

European  corn  borer  (see  Pyrausta). 

Euschistus,  antenna  of,  *32 

Eutermes,  281 

Eiithrips,  *i4 

Evaporation,  369;  adaptations  to,  372;  on 
eclosion,  372;  gradients,  371;  on  hatch- 
ing, 371;  on  life  cycle,  371;  on  metabo- 
lism, 369;  reactions  to,  370 

Everes,  androconium  of,  *7i 

Ewing,  4,  359,  435 

Excrements,  105 

Exner,  on  compound  eyes,  98,  444,  468 

Expiration,  123 


486 


INDEX 


Exuviae,  144 

Eyes,  compound,  *30,   *97;  kinds  of,   *3o; 

sexual  differences  in,  *3i;  simple,  *30, 

*3i 

Fabre,  J.  H.,  316,  466,  468 

Fabre,  J.  L.,  446 

Facets,  *30 

Fat-body,  distribution  of,  112,  *ii3;  func- 
tions, 112;  structure,  112,  *ii3,  *ii4 

Fat-cells,  112,  *ii3 

Faunae  of  islands,  326 

Faunal  realms,  328,  *329 

Faussek,  447 

Felt,  E.  P.,  423,  451,  463 

Female  genitalia,  62,  *6s 

Femur,  *47,  48,  *49 

Fenard,  451 

Fenestrate  membrane,  97,  *98 

Feniseca,  271 

Fernald,  C.  H.,  213,  423,  425,  426 

Fernald,  H.  T.,  426,  432,  477 

Fertilization,  129 

Fidonia,  antennal  sensilla,  *85 

Fielde,  290,  292,  307,  466,  467,  469 

Fielding-Ould,  464 

Filariasis,  265 

Filiform,  *32 

Filippi's  glands,  *76 

Finlay,  253,  464 

Finn,  on  mimicry,  206;  on  warning  colora- 
tion, 199;  460,  461 

Fire  blight,  218 

Fire-flies,  115,  116 

Fischer,  45  8 

Fishes,  insectivorous,  237 

Fitch,  423 

Flagellum,  *32 

Fleas,  *2o,  234 

Fletcher,  429 

Flight,  mechanics  of,  57 

Flint,  W.  P.,  425 

Flogel,  442 

Fluted  scale,  428 

Follicles,  124,  *i27 

Folsom,  433,  436,  447 

Food,  its  effects  on  color,  176,  378;  on  fecun- 
dity, 376;  on  growth,  375;  habits,  373; 
on  hibernation,  378;  on  longevity,  377; 
on  oviposition,  376;  plants,  373;  rela- 
tions, 378;  on  reproduction,  376;  selec- 
tion, 374;  on  sex-determination,  376 


Food  reservoir,  102,  *io4 

Forbes,  H.  O.,  471 

Forbes,  S.  A.,  on  corn  root  louse,  298;  on 
economic  entomologist,  420;  food  of 
Carabidae,  271;  insectivorous  birds, 
239;  insectivorous  fishes,  237;  insect 
oscillations,  243;  424,  462,  463,.  464,  466 

Forbush,  213,  423 

Fore  intestine,  *ioi,  *io2 

Forel,  on  ants,  291;  on  taste,  85;  440,  443, 
444,  445,  467,  469 

Forficulidae,  10 

Formations,  393,  394 

Formative  cells,  69,  *7i 

Formica,  exsectoides,  mounds  of,  2gi;fusca, 
289,  293,  294;  pratcnsis,  eyes  of,  33; 
sangiiinea,  294 

Fossil  insects,  localities  for,  340 

Fossilization,  340 

Free  pupa,  146 

French,  G.  H.,  424 

Frenulum,  54 

Frenzel,  446,  447 

Friese,  459 

Front,  *28,  *29 

Frontal  ganglion,  81,  *82 

FuUer,  467 

Fundament,  131 

Fungi  of  insects,  *2i 7,  *2 1 8 

Furcae,  46,  *48 

Furcula,  62 

Futaki,  266 

Gadeau  de  Kerville,  448 

Gad  flies,  233 

Galapagos  Islands,  Orthoptera  of,  326 

Galea,  *35,  37,  *38 

Galerita,  anal  glands  of,  73;  antenna,  *32; 

sternites,  *47 
Galerucella  luleola,  419 
Galls,  *2i3,  *2i4 
Ganglia,  cephalic,  *43,  80,  *82;  functions  of, 

82 
Ganglion,  structure  of,  81,  *83;  suboesopha- 

geal,   *8i,   *82;  supraoesophageal,  80, 

*82 

Ganglion  cells,  81,  *83 
Ganin,  on  Platygaster,  *is8,  454 
Garman,  426,  456 
Gastric  cffica,  *io2,  *io3,  *I04 
Gastro pacha,  larval  coloration,  177;  stinging 
hair,  *72 


INDEX 


487 


Gastraphilus,  235 

Gastrulation,  *i3o 

Gee,  470 

Gehuchten,  van,  on  digestion,  104;  442,  447 

Gens,  *29 

Geniculate,  *32 

Genitalia,  62;  of  female,  62;  grasshopper, 

*67;  male,  64;  moth,  *66 
Geographical,  distribution,    t,22;   varieties, 

328 
Geological  distribution,  340 
Geometridse,  legs  of  larva%  5  r 
Geotropism,  306 
Gerephemera,  342 
Germ  band,  *i3o;  types  of,  133 
Germ  cells,  129 
Germinal  vesicle,  129 
Gerould,  180,  459,  461 
Gerris,   *i66;  locomotion  of,   168;  thigmo- 

tropism,  304 
Gerstacker,  449 
Gibson,  A.,  429 
Gibson,  W.  H.,  462 
Gill,  T.,  471 
Gillette,  426 
Gills,  *ii8,  *ii9,  169 
Gilson,  447,  450,  456 
Gipsy  moth  (see  Porthetria). 
Girault,  on  numbers  of  eggs,  141 
Gizzard,  102,  *io3 

Glaciation,  its  efifects  on  distribution,  325 
Glands.  72:  accessory,  *i24,  *i26;  alluring, 

74;  repellent,  73;  salivary,  *io6,  *io7; 

silk,  75,  *76,  wax,  74 
Glandular  hairs,  *72,  *73 
Glaser,  114,  449 
Gleason,  474 
Glenn,  356 
Glossa,  *35,  7,t,  *^2 
Glossina,  262,  *263 
Glover,  427 
Golgi,  on  malaria,  248 
Goliathus,  endoskeleton  of,  *48 
Gonapophyses,  *63,  *64 
Gongylus,  210 
Gonin,  454 
Goossens,  439,  440 
Gorgas,  256,  465 
Gortner,  174,  459 
Goss,  473 
Gossard,  425,  426 
Gould,  457 


Graber,  on  chordotonal  organ,  *95;  hal teres, 
loi;  hearing,  94;  431,  437,  439,  443, 
447,  452,  468 

Graham,  269 

Grasshopper,  adaptations,  397;  alimentary 
tract,  *io2;  communities,  394;  geni- 
talia, *67;  hearing,  *94 

Grassi,  on  Termes,  279;  432,  464,  466 

Green  bug  (see  T  0x0  pier  a). 

Gregory,  376 

Gregson,  176 

Grenacher,  on  compound  eye,  98,  100,  443 

Grobben,  432 

Gross,  451 

Grossbeck,  384,  456 

Growth,  144 

Grub,  137 

Griinberg,  451,  465 

Gryllidse,  10 

Grylloblattidae,  10 

Gryllotalpa,  leg  of,  *5o;  maternal  care,  76 

Gryllus,  sense  hairs,  *9o;  stridulation,  92 

Gula,  29,  37 

Giinther,  445 

Guy6not,  376 

Gynandromorphism,  127,  *i28 

Gyrinidae,  eyes  of,  *30 

Gyrinus,  locomotion  of,  168;  respiration, 
169;  tracheal  gills,  *ii8 

Haase,  432,  439,  449,  460 

Hsemolymph,  no 

Hagen,  279,  430,  455,  457 

Hairs,  development  of,  *68,  69;  functions, 

69;  histology,  *6g;  modifications,  *68; 

pollen-gathering,  *6o,  *227;  protective, 

245;  tenent,  *72 
Halisidota,  distribution  of,  336 
Halobaies,  170 
Halteres,  53,  loi 

Hamilton,  on  holarctic  beetles,  331,  471 
Hammar,  358,  360 
Hammond,  A.  R.,  454 
Hammond,  J.  H.,  Jr.,  312 
Hamuli,  54 

Handlirsch,  8,  347,  433,  434,  435,  474 
Hansen,  432,  433,  436 
Harmolita,  273 
Harned,  426 
Harpactophagous,  373 
Har pains,  labium  of,  *38;  maxilla,  *38 
Harris,  423,  476 


INDEX 


Hart,  456,  474 

Hartman,  469 

Harvey,  425 

Hatching,  141 

Hatschek,  452 

Hauser,  on  smell,  87,  443 

Haushaltef,  268 

Haviland,  on  termites,  281 

Hawaii,  beetles  of,  326;  Hymenoptera,  327 

Hayward,  on  stridulation,  93 

Head,  28;  segmentation  of,  *43 

Headlee,  356,  359,  364,  367,  370,  372,  425, 

475-376 
Hearing,  94 

Heart,  *io9,  *iio,  *iii 
Heath,  on  Termopsis,  278,  467 
Heer,  on  fossil  insects,  341,  473 
Heider,  452,  454 
Heilprin,  472 
Heim^  462 
Heinemann,  448 
Heliconiidae,  mimicry,  202 
HcUophila  (see  Cirphis). 
Heliotropism,   306;   machine    to   illustrate, 

311 
Helm,  446 
Hemelytra,  53 

Hemerocampa,  parasites  of,  274 
Hemimeridae,  10 

Hemimerus,  *ii;  hypopharynx  of,  *38 
Hemiptera,  16;  mouth  parts,  *39;  odors,  73; 

origin,  23 
Henking,  450,  452 
Henneguy,  431 
Hennings,  370 
Henshaw,  430 

Heptagenia,  hypopharynx  of,  *;,& 
Hermaphroditism,  125 
Herms,  425,  465,  470,  474 
Herrick,  424,  426,  477 
Hesse,  445 

Hessian  fly  (see  Mayetiola). 
Hctarius,  300 
Heterocera,  18 
Heterogeny,  127 
Heterogony,  358 
Heterometabola,  138 
Heterophaga,  19 

Heteroptera,  *i6;  spiracles  of,  60 
Hewitt,  375,  429,  436,  477 
Hexagenia,    *i^,    14;   male   genitalia,    *65; 

tracheal  gills,  *ii8 


Hexapoda,  defined,  4 

Heymons,  139,  433,  439,  451,  453 

Hibernation,  361 

Hicks,  on  olfactory  pits,  88 

Hickson,  444 

Higgins,  456 

Hildebrand,  384 

Hilton,  441 

Hind  intestine,  *io2,  *io4 

Hinds,  354,  355,  359,  360, 361,  366,  367,  377, 

378,  426 
Histogenesis,  160 
Histolysis,  160 
Hochreuther,  445 
Hodgkiss,  424 
Hoffbauer,  438 
Holarctic  realm,  331 
Holcaspis,  galls  of,  *2i3,  *2i4 
Holmes,    69,  470 
Holmgren,  436,  443,  450,  451,  467 
Holometabola,  137 
Holopneustic,  117,  168 
Holoptic,  *32 
Homoptera,  16 
Honey,  285,  413 
Honey  ants,  *294 
Honey  bee  (see  Apis  mellifera). 
Hopkins,  A.  D.,  426,  429 
Hopkins,  F.  G.,  on  pigments,  175,  458 
Hoplia,  sexual  coloration  of,  185 
Horn,  on  Cicindela,  189 
Houghton,  426 
House  fl}^  (see  Miisca). 
Houser,  425 
Howard,  274,  338,  423,  428,  429,  431,  464, 

465,  466,  472,  477 
Howes,  470 

Hubbard,  on  parasitism.  274 
Huber,  on  wax,  282 
Hudson,  471 
Humboldt ia,  232 
Hunter,  S.  J.,  356,  426,  431 
Hunter,  W.  D.,  354,  355,  359,  360,  361,  366, 

367,  368,  375,  376,  378,  428,  429 
Huxlej^,  450 
Hyaloplasm,  78 

Hyatt  and  Arms,  21,  160,  431,  432,  454 
Hybernia,  176 
Hydno phylum,  *232 
Hydrophilus,  *i5,   *i66;  antennae,  33;   leg, 

■•167;  locomotion,  166;  male  genitalia, 

*65;  respiration,  169 


489 


Hydrotropism,  303 

Hydrous,  tergites  of,  *46 

Hylastinus,  338 

Hylobius,  glandular  hairs  of,  *72 

Hymenoptera,  defined,  18;  cephalic  glands, 
107;  eyes  of  sexes,  *32;  internal  meta- 
morphosis, 162;  mouth  parts,  *42; 
ocelli,  31;  origin,  25;  sounds,  91;  wing, 
*56 

Hypatus,  364 

Hypera,  338 

Hypermetamorphosis,  156 

Hyperparasitism,  274 

Hyphze,  217 

Hyphantria,  246 

Ilypoderma,  lar\'a  of,  *i42;  lincala,  habits 
of,  235;  losses  through,  411 

Hj-podermal  colors,  174 

HjTJodermis,  *67,  *68 

Hypognathous,  11 

Hypopharynx,  *ss,  37,  *38,  *4i 

I  eery  a,  428 

Ichneumonid^,  *2  72 

Ileum,  *io5 

Imaginal  buds,  *i6r,  *i62 

Imago,  137 

Imms,  477 

Incomplete  metamorphosis,  138 

Incubation,  358 

Indirect  metamorphosis,  137 

Ingenitzky,  451 

Injurious  insects,  410;  introduction  of,  416 

Ino,  antennal  sensilla  of,  *85 

Inquilines,  215,  281 

Insecta,  defined,  4 

Insectivorous  birds,  239;  fishes,  237;  plants, 
216;  vertebrates,  236 

Inspiration,  123 

Instar,  140 

Instinct,  313;  apparent  rationality  of,  314; 
basis  of,  313;  flexibility,  316;  inflexi- 
bility, 315;  modifications,  315;  origin, 
317;  stimuli,  314;  and  tropisms,  318 

Integument,  65 

Intelligence,  318 

Interactions  of  organisms,  379 

Intercalary,  appendages,  *i32;  neuromere, 
*43;  segment,  44 

Interglacial  beetles,  346 

Interrelations,  of  insects,  270;  of  orders,  20 

Intima,  *76,  106,  *i2i 


Iphiclides  ajax,  polymorphism  of,  181 
Iridescence,  172 
Iris  pigment,  *96,  *97 
Iris  versicolor,  *2  20,  *2  2i 
Irritants,  246 
Isaria,  217 

Isia,  cocoon  of,  148;  hairs,  69,  146;  hiberna- 
tion, 361;  molts,  145 
Island  fauna?,  326 
Isolation,  328 
Isoptera,  11 

Isosoma  (see  HarmoUta). 
Isotropic,  78 

Ithomiinae,  mimicry,  202,  203 
Itonididse,  galls  of,  214;  paedogenesis,  128 

Jackson,  C.  F.,  431 

Jackson,  T.  W.,  465 

Jacobi,  461,  472 

James,  W.,  468 

Janet,  on  Atelura,  *3oo;  on  muscles,  *78; 
436,  4395  440,  442,  466,  467 

Japan,  415 

Japanese  beetle  (see  PopiUia). 

Japyx,  9,  22;  spiracles  of,  60 

Jennings,  469 

Johannsen,  456,  465 

Johnson,  R.  H.,  459 

Johnson,  W.  G.,  426,  477 

Jordan,  436 

Jorschke,  445 

Judd,  on  food  of  bluebird,  242;  mimicry, 
208;  protective  adaptations,  245;  pro- 
tective resemblance,  198;  warning  col- 
oration, 199;  460,  463,  464 

Jugum,  54 

Jurassic  insects,  341,  345 

Kala-azar,  269 

Kallima,  protective  resemblance  of,  *i94 

Kanthack,  464 

Kapzov,  441 

Kathariner,  469 

Katydid,  stridulation  of,  93 

Kellogg,  on  Mallophaga,  233;  mouth  parts, 

40;   phototropism,   310;   pilifers,    */\o; 

scales,    70,    172;   swarming,    286;   431, 

43S>  436,  458 
Kenyon,  432,  443 
Kidney  tubes,  *io8 
Kielich,  442 
Kilborne,  269 


490 


INDEX 


Kingsley,  on  Arthropoda,  7 

Kirby,  431,  432 

Kirkland,  463 

Klemensiewicz,  440 

Kluge,  451 

Knuppel,  447 

Koch,  250 

Kochi,  436 

Koestler,  442 

Kolbe,  431 

Kolliker,  442 

Korotneff,  452 

Korschelt,  450,  452,  453,  454 

Kowalevsky,  447,  448,  451,  454 

Kraepelin,  436 

Krancher,  449 

Krause's  membrane,  *78 

Krogh,  on  temperature- velocity,  357;  pupal 

development,  359 
Krukenberg,  67 
Kulagih,  41,  436,  453,  454 

Labellum,  *4i,  *42 

Labial,  neuromere,  *43,  81,  135;  segment,  44 

Labium,  29,  *-s5  37,  *38,  *39*4i 

Labrum,  *29,  *35,  *39 

Lac,  75,  413 

Lachnosterna,  antenna  of,  *32;  cocoon,  148; 

larva,  *i42 
Lacinia,  *35,  37,  *38 
Lagoa,  legs  of,  51;  stinging  hairs,  *73 
Lamarck,  on  instinct,  317 
Lameere,  455 
Lamellate,  *32 
Landois,  449 
Lang,  435 

Langley,  on  luminosity,  115 
Lankester,  433 
Larvae,  137;  adaptations  of,  145;  legs,  50; 

nutrition,  145;  parasitic,  275;  types  of, 

*I42 

Lasiiis,  age  of,  289;  nest,  291;  parthenogene- 
sis, 128 
Lathrop,  470 

Laveran,  on  malaria,  248,  465 
Laverania,  248,  *249 
Leachia,  eyes  of,  *3o 
Leaping,  52 
LeBaron,  424 
LeConte,  470 
Lee,  on  halteres,  loi;  444 
Legs,  adaptations  of,  48,   *5o;  larval,   50; 


Legs,  mechanics,  *52;  muscles,  *S5',  seg- 
ments, *49 

Lendenfeld,  von,  437,  441 

Leng,  456 

Lens,  *96 

Leonard,  477 

Leopard  moth  (see  Zeiizera). 

Lepidocyrtus,  scales  of,  70 

Lepidoptera,  defined,  18;  internal  metamor- 
phosis, *i62;  molts,  145;  mouth  parts, 
*4o;  origin,  25;  reproductive  organs, 
*i24,  *i 26;  silk  glands,  * 76; spiracles, 60 

Lepidotic  acid,  176 

Lepisma,  *g,  21,  *i42;  spiracles  of,  60 

Leptinotarsa  decemlineata,  aestivation,  366; 
color  pattern,  175,  186,  *i9i;  distribu- 
tion, 336,  338;  dorsal  wall,  *i35;  ento- 
derm, *i36;  folding  of  wing,  *57; 
hibernation,  365;  spread,  338;  varia- 
tion in  coloration,  *i9i 

Leptocoris,  339 

Leptosphceria,  219 

Leptospira,  255 

Lerema,  ocellus  of,- 31 

Leuckart,  451 

Leucocytes,  *iio,  114,  160 

Leydig,  442,  446,  450 

Libellula,  *i4,  *i42 

Lice,  biting,  *i2,  223;  sucking,  *i5,  234 

Life  zones,  332,  *sss 

Light,  351;  on  activity,  352;  growth,  352; 
pigmients,  177 

Ligula,  *38  ' 

Limacodes,  scale  of,  *6g 

Una,  color  changes  of,  190;  distribution, 
336;  germ  band,  *i3i;  glands,  74 

Linden,  von,  458,  459 

Lingua,  ^38 

Link,  445 

Linnaeus,  on  orders  of  insects,  7 

Lintner,  423,  476 

Lithomantis,  *2,AZ 

Livingston,  369,  389,  391,  476 

Lloyd,  456 

Locality  studies,  319 

Lochhead,  477 

Locustidae,  10;  molts  of,  144 

Locy,  446 

Lodeman,  477 

Lodge,  470 

Loeb,  302,  304,  305,  306,  308,  309,  311,  373, 
468,  469,  470,  476 


491 


Lomechusa,  *2<)g 

Longitudinal  muscles,  *io5,  io6 

Lord,  268 

Lorum,  *42 

Losses  through  insects,  410 

Lovell,  445 

Low,  on  malaria,  250 

Lowe,  424 

Lowne,  435,  443,  444,  450 

Lubbock,  on  ants,  289,  290,  292,  294,  297, 
298,  307;  larval  characters,  146;  mus- 
cles, 78;  vision,  99;  432,  441,  443,  444, 
454,  462 

Lucanus,  cocoon  of,  148;  dorsal  vessel,  *io9; 
spiracles,  *i2o 

Lucilia,  *3o6 

Lugger,  425 

Liihe,  465 

Luks,  442 

Luminosity,  114 

Lund,  448 

Lutz,  383,  385,  432,  456 

Lycana,  facets  of,  31 

Lycaenid  larvae,  alluring  gland  of,  74 

Lyais,  mimicked,  206,  207 

Lyon,  304 

Lyonet,  on  muscles,  78;  435,  441 

MacGillivray,  456 

Machilis,  9,  21;  abdominal  appendages,  *6i; 
nervous  system,  *8i;  scales,  *69; 
spiracles,  60 

Macloskie,  449,  455 

Macrosiphum  pisi,  interactions  of,  380 

Madeira  Islands,  beetles  of,  326 

Maggot,  137 

Malacopoda  (see  Onychophora). 

Malacosoma,  eggs,  141 

Malaria,  248,  ^249 

Male  genitalia,  64,  *65,  *66 

Mallock,  A.,  444 

Mallock,  H.  R.  A.,  438 

Mallophaga,  *i2,  233 

Malpighian  tubes,  *io8 

Mammen,  450 

Mandibles,  *35;  adaptations  of,  *2>^;  Culex, 
*4i;  Lepidoptera,  *4o 

Mandibular,  neuromere,  *43,  81,  135;  seg- 
ment, 44 

Mandibulate  mouth  parts,  *35;  orders,  34 

Mandus,  461 

Mann,  141 


Manomcra,  *iq^ 

Manson,  on  filariasis,  265;  malaria,  250;  465 

Mantida;,  10,  270 

Mantis  pa,  24;  metamorphosis  of,  *i43 

Maples,  insects  of,  212 

Marchal,  136,  453 

Marey,  on  wing  vibration,  58;  437,  438 

Ma'T  gar  opus,  269 

Marine  insects,  170 

Mark,  E.  L.,  444 

Marlatt,  428,  429 

Marshall,  on  adaptive  coloration,  206,  207, 
460,  461 

Martin,  438 

Mast,  470 

Maternal  provision,  276 

Maturation,  129 

Maxillae,  37,  *38 

Maxillary,  neuromere,  *43,  81,  135;  seg- 
ment, 44 

Maxillulae,  36 

Mayer,  A.  G.,  on  color  pattern,  188;  Papilio, 
179;  scales,  71 ;  441,  458,  460 

Mayer,  A.  M.,  on  Culex,  94,  443 

Mayer,  P.,  432,  443 

Mayetiola  destructor,  distribution,  368; 
evaporation  on,  371;  longevity,  377; 
losses  through,  410;  moisture  on,  365 

May  fly,  male  genitalia  of,  *65;  wings,  *56 

McAtee,  461 

McColloch,  359,  367,  368 

McCook,  on  ants,  291,  294,  295,  296,  297, 
466 

McDermott,  449 

McEwen,  311 

Mclndoo,  90,  445,  446,  470 

Mealworm  (see  Tenebrio). 

Meconium,  152 

Mecoptera,  defined,  17;  origin,  24 

Media,  *54,  55 

Median  segment,  44,  61 

Meek,  436 

Megackile,  hairs  of,  *68 

Megalodacnc,  antenna  of,  *32 

Meganeura,  344 

Megarhyssa,*  272 

Megilla  (see  Ceratomegilla). 

Melander,  426,  467 

Melanism,  180 

Melanoplus,  alimentary  tract  of,  *io2; 
facets,  *3o;  genitalia,  *6y;  mandible, 
*36;  respiration,  122;  skull,  *29 


492 


INDEX 


Melanotus,  larva  of,  *i42 

Meldola,  460 

Melissodes,  225 

Melnikow,  451 

Melo'e,  antenna  of,  2,3',  hypermetamorphosis, 
156 

Melolontha,  male  reproductive  system, 
*i24;  olfactory  pits,  88 

Mendelism,  209 

Menopon,  *i2 

Mentum,  *35,  37 

Merriam,  on  life  zones,  332,  471,  472 

Merrifield,  457,  458 

Merrill,  425 

Mesenchyme,  *i36 

Mesenteron,  *io2,  *io3,  *io4,  136 

Mesnil,  465 

Mesoderm,  130,  *i36 

Meso-entoderm,  *i3i 

Mesothorax,  44 

Metabola,  140 

Metallic  colors,  173 

Metamorphosis,  defined,  137;  external,  137; 
internal,  160;  significance,  159;  sys- 
tematic value,  24 

Metatarsus,  *2  28 

Metathorax,  44 

MetschnikoflF,  446,  451,  454 

Miall,  on  chitin,  66;  muscles,  78,  431,  435, 
442,  450,  454,  456 

Miaslor,  paedogenesis  of,  *i28 

Michels,  442 

Michelson,  173,  174 

Microcentrum,  stridulation  of,  92,  *93 

Microphaga,  373 

Micropteryx,  mouth  parts  of,  40 

Micropyle,  129,  141 

Mid  intestine,  *io2,  *io3,  *io4 

Milkweed,  pollination  of,  221,  *2  22 

Mimicry,  201;  evolution  of,  208 

Minot,  440 

Miocene  insects,  341,  345 
Mitchell,  465 

Moisture,  364;  its  effects  on  activity,  365; 
aestivation,  366;  coloration,  178;  eclo- 
sion,  365;  hibernation,  365;  metabo- 
lism, 364;  mortality,  365;  oviposition, 

36s 
Molanna,  *i7 
Moles,  insectivorous,  236 
Moller,  on  leaf-cutting  ants,  295,  462 
Mollock,  on  vision,  99 


Molting,  144,  359 
Molts,  number  of,  144 
Moniliform,  *3,2 
Mononychus,  226 
Monophagous,  373 
Mordella,  facets  of,  31 
Mores,  393 

Morgan,  C.  Lloyd,  207,  468,  469 
Morgan,  H.  A.,  426 
Morgan,  T.  H.,  377,  469,  474 
Morpho,  scales  of,  70,  172 
Morrill,  354 

Morse,  A.  P.,  396,  397,  472,  474 
Mosaic  diseases,  319  ~ 

Mosquito,  antennae  of,  *34;  hearing,  94; 
hibernation,  311;  locomotion  of  larvae, 
167;  in  relation  to  malaria,  248,  250; 
mouth  parts,  *4i;  respiration,  169; 
tropisms,  311 
Moulton,  461 

Mouth  parts,  dipterous,  *4i;  hemipterous, 

*39;  hymenopterous,    *42;  lepidopter- 

ous,  *4o;  mandibulate,  *35;  orthopter- 

ous,  *35;  suctorial,  38 

Muir,  23 

Miiller,   F.,   on   mimicry,   204;   wings,   53; 

460 
Muller.  H.,  462 

Miiller,  J.,  mosaic  theory  of,  98,  443 
Miillerian  mimicry,  203,  204 
Murray,  471 

Miisca,  egg  of,  *i39;  facets,  31;  fungus  of, 

*2i8;    molts,    145;    oviposition,    365; 

ovum,    *i29;   in   relation   to    t>'phoid 

fever,  257,  258,  259 

Muscidae,  cardiac  valve  of,  *io4;  imaginal 

buds,  *i6i 
Muscles,  circular  and  longitudinal,  ro6;  of 
cockroach,  *53,  *77;  of  leg,  *sy,  num- 
ber, 77;  structure,  *78;  of  mng.  *so 
Muscle-tension  theory,  311 
Muscular,  power,  79;  system,  77 
MiUilla,  stridulation  of,  92 
Muttkowski,  456 
Mycetophaga,  374 
Myrientomata,  6,  *7 
Myriopoda,  5 
Myrmecocystus,  295 
Myrmecodia,  232 

Myrmecopkana,  mimicry,  by,  *205 
Myrmecophilism,  297        .      ' 
Myrmedonia,  300 


493 


Myrmeleon,  digestive  system  of,  *io3;  pre- 

daceous,  270;  silk  glands,  77 
Myrmica,  *2gg 
Mystacides,  androconia  of,  72 

Nagana,  263 

Nagel,  444 

Nearctic  realm,  331 

Necrophagous,  373 

Necrophorus,  236,  276 

Needham,  54,  104,  424,  438,  447,  456, 
462 

Nelson,  453 

Nemobius,  leg  of,  *5o 

Neotropical  realm,  331 

Nepa,  respiration  of,  169 

Nephrocyte,  1 10 

Nerves,  of  head,  81,  *82;  structure,  *8i 

Nervous  system,  80;  development  of,  133, 
*i3S 

Nervures,  54 

Neuration,  *54,  *55,  *56 

Neuroblasts,  *i35 

Neuromeres,  44,  134;  of  head,  *43,  So 

Neuroptera,  defined,  17;  metamorphosis  of, 
24,  *i43 

Newbigin,  458,  460 

Newcomer,  362 

Newell,  A.  G.,  440 

Newell,  W.,  426 

New  Mexico,  insect  communities  in,  399 

Newport,  on  metamorphosis,  162;  muscles, 
78;  435,  441,  442 

Newton,  442 

NicoUe,  267 

Noguchi,  255,  256 

Northrop,  373,  476 

Notolophiis,  olfactory  organs  of,  89 

Notoneda,  *i66;  locomotion  of,  *i66;  res- 
piration, 169 

Notum,  45 

Novius,  275,  412,  428 

Nucleolus,  129 

Number  of  insects,  27 

Nuttall,  464 

Nymph,  139 

Oaks,  insects  of,  212,  410 
Oberea,  eyes  of,  30 
Obtect  pupa,  *i47 
Occipital  foramen,  29,  *30 


Occiput,  29 

Ocelli,  *3i;  structure  of,  95;  vision  bv, 
96 

Ockler,  437 

Ocular,  neuromere,  *43;  segment,  44 

Odonata,  abdominal  segments  of,  60;  copu- 
lation of,  65;  defined,  14;  ocelli,  31; 
origin,  23;  spiracles,  60 

Odors,  73;  efficiency  of,  246 

Odynertcs,  225 

(Ecanlkus,  abdominal  appendages  of,  61, 
*i33;  embryo,  *i33;  stridulation,  93 

(Ecophylla,  291 

(Edipoda,  dorsal  vessel  of,  *iio 

(Eneis,  distribution  of,  325 

(Enocytes,  *ii4 

(Esophageal  commissures,  *82 

Esophagus,  *io2,  *io3,  *io4 

(Estridae,  234 

O'Kane,  426,  477 

Olfactory  organs,  87,  *88,  *89 

Oligocene  insects,  341 

Oligophagous,  373 

Oligotoma,  *ii 

Ommatidium,  *97,  *98 

Onthophagus,  mandible  of,  *t,6 

Onychophora,  2.  *3 

Ophthalmia,  269 

Ore  hell  mum,  stridulation  of,  92 

Orders  of  insects,  7,  *25 

Oriental  realm,  332 

Origin  of  arthropods,  *8;  of  insects,  6 

Oroya  fever,  269 

Orthoptera,  abdominal  segments  of,  60; 
defined,  9;  ecological  succession,  408; 
origin,  22;  stridulation,  92,  *93 

Osborn,  426,  477 

Osburn,  384,  386,  387,  456 

Osmeterium,  *74 

Osmia,  225 

Osmoderma,  cocoon  of,  148 

Osten-Sacken,  440 

Ostium,  *i09,  *iio 

Oudemans,  450 

Oustalet,  455 

Ovaries,  123,  *i26 

Ovariole,  125 

Oviducts,  125,  *i26 

Ovipositor,  62,  *63,  *67 

Ovogenesis,  129 

Ovum,  of  Musca,  *i29;  Vanessa,  *i2  7 

Ox-warble,  *i42,  235 


494 


Paasch,  443 

Packard,  on  Anophthalmus,  100;  Arthro- 
poda,  7;  classification,  7;  Mantispa, 
143;  olfactory  pits,  88;  relationships  of 
orders,  22;  segmentation,  27;  types  of 
larvae,  142;  wings,  53;  423,  427,  431, 
432,  433,  439,  442,  444,  449,  454,  455, 
461,  476 

Pasdogenesis,  128 

Palaearctic  realm,  331 

Palaoblatlina,  *34i 

Palaeodictyoptera,  347 

Palmen,  449,  450 

Palmer,  464 

Palpifer,  *35,  37,  *38 

Palpiger,  *35,  37,  *38 

Palpus,  *2,S,  37,  *38,  *40 

Pankrath,  444 

Panorpidae,  18;  legs  of,  51 

Pantophagous,  373 

Papilio,  colors  of,  179;  egg,  *i39;  facets,  31; 
head  of  pupa,  *i47;  melanism,  180; 
mimicry,  202,  205;  osmeterium,  *74; 
protective  resemblance,  196;  cenea, 
mimicry  by,  202,  205 

Paraglossa,  *s5,  37,  *38 

Paragnaths,  37 

Paralysis,  infantile,  269 

Paraponyx,  *ii9,  170 

Paraptera,  46 

Parasita,  defined.  16 

Parasitic  insects,  233,  271,  275;  in  relation 
to  birds,  245 

Parasitism,  235,  271;  economic  importance 
of,  274 

Parcohlatta,  mouth  parts  of,  *35 

Parker,  on  phototropism,  309,  469 

Parks,  354,  475 

Parman,  352,  363,  365,  475,  476 

Parrott,  424 

Parthenogenesis,  127,  216,  286,  290,  358 

Passalus,  cocoon  of,  148;  stridulation,  91 

Patagia,  45 

Patch,  E.  M.,  425 

Patten,  B.  M.,  470 

Patten,  W.,  444,  452 

Pawlovi,  443 

Pawlowa,  448 

Payne,  311 

Peacock,  437 

Peairs,  426,  431,  475,  477 

Pea  louse  (see  Macrosiphum). 


Peck,  W.  D.,  423 

Peckham,  on  behavior,  316,  318,  319,  466, 
467,  469 

Pecten,  *228 

Pectinate,  *32 

Peciinophora  gossypiella,  419 

Pedicel,  *32 

Pediculidae,  234 

Pediculus,  *i5,  234,  267,  268 

Pelocoris,  leg  of,  *5o 

Penis,  64,  *65,  124 

Pepsis,  277 

Perez,  455 

Pericardial,  ceUs,  no;  chamber,  *io9,  *i23 

Peripatus,  characters  of,  2,  *3,  5;  systematic 
position,  5 

Periplaneta,  olfactory  pits  of,  88 

Peripodal,  cavity,  161;  membrane,  161;  sac, 
161 

Peritrophic  membrane,  106 

Perla,  olfactory  pits  of,  88 

Perlidae,  *i3,  14;  nymph,  *i42;  tracheal 
gUls,  *ii8 

Permian  insects,  344 

Peterson,  371,  437,  476 

Petiolata,  19 

Pettigrew,  437 

Pettit,  426 

Petunia,  *2  25 

Peytoureau,  439,  451 

Pflugstaedt,  438 

Phagocytes,  114,  160 

PhancBus,  legs  of,  49,  *5o 

Pharynx,  102 

Phasmidas,  10,  *i95 

Philiptschenko,  44 

PhiUips,  E.  F.,  429 

Phillips,  W.  J.,  368 

Phlebotomus  fever,  269 

Phormia,  antenna  of,  *32;  eyes,  *3i;  meta- 
morphosis, *i38;  phototropism,  310 

Phosphorescence,  114 

Pholinus,  luminosity  of,  *ii5 

Photogeny,  114 

Photopathy,  307 

Photophil,  307 

Photophob,  307 

Phototaxis,  307 

Phototropism,  306 

Photurts,  116 

Phragmas,  46,  *48 

Phthirius,  234 


INDEX 


495 


Phyciodes,  coloration  of,  178,  *i82 

Phylloxera,  350,  410,  416 

Phylogeny,  5,  *8,  *2$ 

Phytonomus,  spread  of,  338 

Phytophaga,  *i9 

Phytophagous,  373 

Pictet,  on  coloration,  176,  179 

Piepers,  460 

Pierce,  24,  157,  354,  360,  368,  375,  376,  378, 
434,  463,  466 

Pieris,  color  sense  of,  100;  dispersion,  322; 
.fat-cells,  *ii3;  imaginal  buds,  *i62; 
olfactory  organs,  *9o;  scale,  *6g;  napi: 
temperature  experiments  on,  182;  pro- 
todice:  sexual  coloration  of,  *i84; 
rapa:  androconium  of,  *7i;  developing 
wing,  *i63;  distribution,  338;  eggs, 
*i4o;  food  plants,  213;  hair,  *68;  larval 
tissues,  *ii3;  pupal  coloration,  177; 
wing  vibration,  59;  xanthodice,  distri- 
bution of,  322 

Pigmental  colors,  174 

Pigments,  of  eyes,  *96,  *97,  *98,  *99;  nature 
of,  175;  of  Pieridc-e,  175 

Pilifers,  *4o 

Pimpla,  274 

Pine,  insects  of,  212 

Ping,  476 

Pinguicula,  216 

Pink  boll  worm  {set  PecHnophora). 

Placodeum,  *85 

Plague,  260 

Planta,  *2  28 

Plant  lice  (see  AphididcB). 

Plants,  diseases  of,  218;  insectivorous,  216; 
insects  in  relation  to,  212 

Plasma,  no 

Plasmodium,  248 

Plateau,  on  color  sense,  100;  muscular 
power,  79;  respiration,  123;  441,  444, 
446,  449,  468 

Platephemera,  *342 

Platheniis,  abdominal  appendages  of,  *66; 
antenna,  *32 

Plalygaster,  hypermetamorphosis  of,  146, 
*IS8 

Platypsyllus,  234 

Platyptera,  defined,  10;  origin  of,  22,  *2$ 

Plecoptera,  defined,  14,  *i3;  nymph,  *i42; 
origin,  22,  *25 

Pleistocene  insects,  341 

Pleurites,  *45,  *47 


Pleuron,  45 

Plotnikow,  441 

Pocock,  432 

Podical  plate,  *()^ 

Podisus,  egg  of,  *i39;  predaceous,  *27o 

Pcecilocapsus,  color  changes  of,  190 

Pogonomytmex,  297 

Polar  bodies,  *i29 

Poletajew,  449,  455 

Poliomyelitis,    269 

Polistes,  behavior  of,  316,  321;  habits,  288; 
wing  vibration,  *58 

Poliles,  on  Iris,  *226 

Pollenizers,  insect,  225 

Pollination,  219,  225;  of  Iris,  *22o;  milk- 
weed, 221,  *222;  orchids,  221;  Yucca, 

222,   *224 

Pollinia,  *22  2 

Polyhia,  287 

Polyembryony,  136 

Polyergus,  294 

Polygoneutic,  182 

Polygonia,  dimorphism  of,  180;  egg,  *i39 

Polymorphism,  289 

Polynema,  158 

Polyphagous,  373 

Polyphemus  (see  Telea). 

Polyphylla,  assembling  of,  90 

Polyrhachis,  291 

Pomace  flies  (see  Drosophila). 

Pompilus,  behavior  of,  316,  319 

Popillia  japonica,  418 

Porthetria  dispar,  damage  by,  416;  distribu- 
tion by  winds,  368;  gynandromor- 
phism,  *i28;  tracheoles,  *i2i 

Postclypeus,  29 

Postgense,  29 

Postscutellum,  *45,  *46 

Potato  beetle  (see  Leptinolarsa). 

Pouchet,  468 

Poulton,  on  adaptive  coloration,  206,  207, 
209;  on  colors  of  larvas  and  pupae,  177; 
454,  457,  458,  459,  460,  461 

Powell,  139,  455 

Pratt,  454,  455 

Precipitation,  366 

Predaceous  insects,  233,  *27o;  in  relation 
to  birds,  245 

PreU,  434 

Premandibular,  appendages,  *i32;  segment, 
*43,  44 

Pressure,  363 


496 


INDEX 


Pricerj  467 
Primitive  insects,  20 

streak,  130 
Primordial  insect,  21 
Priomis,  assembling  of,  91;  eggs,  141 
Proboscis,  *40 

Procephalic  lobes,  *i32,  *i33 
Prochnow,  438,  445 
Proctodaeum,  *io2,  104,  131 
Proctotrypidae,  27,  274 
Prodoxus,  224 
Prodryas,  *346 
Prognathous,  11 
Promethea  (see  Callosamia). 
Pronotum,  *46 
Pronuba,  *223,  *224 
Propodeum,  44 
Propolis,  283 
Prolapteron,  6 
Protective,     adaptations,     245;     mimicry, 

*20i,  206;  resemblance,  *i94,  198 
Prothorax,  44 
Protocerebrum,  80,  135 
Protoparce,  head  of  moth,  *4o;  larva,  *si; 

moth,  *225;  parasitized  larva,  *273 
Protura,  6,  *7 

Proventriculus,  *io2,  *io3,  *io4 

Pseudocercus,  *6i,  62,  *65 

Pseudocone,  *98 
Pseudomyrma,  230 

Psocidae,  *i2 

Pteromalus,  oviposition  of,  376 

Pteronarcys,  *i3;  tracheal  gills  of,  119 

Pterygota,  9 

Ptilodadyla,  antenna  of,  *32 

Pulvillus,  48,  *5i 

Punktsubstanz,  81 

Punnett,  209,  461 

Pupfe,  137,-146;  emergence  of,  152;  protec- 
tion, 148;  respiration,  147 

Pupal  stage,  significance  of,  159,  162 

Puparium,  147,  372 

Pupation  of  a  caterpillar,  147,  *i49 

Putnam,  on  habits  of  Bombus,  287 

Pyloric  valve,  104 

Pyrausta  nubilalis,  spread  of,  418 

Pyrophila,  thigmotropism  of,  304 

Pyrophorus,  luminosity  of,  115 

Pyrrharctia  (see  Isia). 

Quaintance,  359,  366,  372,  428 
Quaternary  insects,  346 


Quayle,  425 
Quedkis,  300 
Queen,  honey  bee,  *282;  termite,  *278 

Radius,  *54 
Rddl,  469 
Rainfall,  366 

Ranatra,  166;  phototropism  of,  311;  respira- 
tion, 169 
Rand,  463 
Raschke,  449 

Rath,  vom,  on  sense  hairs,  *9o;  444,  445 
Rathke,  449 

Rationality,  apparent,  314;  lack  of,  321 
Rau,  352,  470 
Realms,  faunal,  328,  *329 
Reaumur,  de,  435 
Receptaculum  seminis,  125,  *i26 
Recognition  markings,  211 
Rectal  respiration,  119,  170 
Rectum,  105 
Recurrent  nerve,  81,  *83 
Redikorzew,  on  ocelli,  *96,  445 
Redtenbacher,  437 
Reed,  on  yellow  fever,  253,  465 
Rees,  van,  454 
Reichenbach,  on  ants,  128 
Relapsing  fever,  267 

Relationships,    of    arthropods,    4,    *7;    oi 
orders,  20,  *25 

Repellent  glands,  73 

Replacements,  190 

Reproduction,  of  plant  lice,  358 

Reproductive  system,  123 

Respiration,  122,  147,  155 

Respiratory  system,  116,  *ii7 

Reticitlitermes,  279,  281 

Retina,  *g6 

Retinula,  *g(),  *g% 

Renter,  445 

Rhabdom,  *g(),  97,  *98 

Rheotropism,  304 

Rhipiphorus,  156 

Rhopalocera,  18 

Rhyphus,  *5S 

Ricketts,  267,  269 

Riley,  C.  F.  C,  304,  470,  474,  476 

Riley,  C.  V.,  on  hypermetamorphosis,  156; 
losses  through  insects,  410;  pollination 
of  Yucca,  222;  pupation,  147;  377,  4io> 
412,  425,  427,  454,  462 
Riley,  W.  A.,  139,  465 


497 


Rimsky-Korsakow,  6,  434 

Ritter,  438 

Robertson,  462 

Robin,  food  of,  240 

Rocky  Mountain  locust,  dispersion  of,  322; 

as  food  of  birds,  243 
Rocky  Mountain  spotted  fever,  269 
Rolfs,  426 
Rollet,  442 

Romanes,  on  instinct,  317,  468 
Rosenau,  269 
Ross,  on  malaria,  250,  464 
Rossig,  462 
Rostrum,  39 
Roziles,  *296 
Ruggles,  425 
Ruland,  444 

Sadones,  450,  455,  456 

Saliva,  of  Dytiscus,  107;  mosquito,  107 

Salivary  glands,  *io6,  *io7 

Sambon,  on  malaria,  250 

Samia  cccropia,  antennas  of,  *2,y,  cocoon, 
*i5i;  egg,  141;  food  plants,  213;  geni- 
talia, *66;  head  of  larva,  *74;  Malpigh- 
ian  tubes,  *io8;  ocelli,  *3i;  odor,  74, 
scales,  *7i 

Sanderson,  356,  359,  360,  362,  365,  366,  370, 
426,  431,  474,  477 

Sandias,  466 

San  Jose  scale  insect  (see  Aspidiotus  perni- 
ciosiis) . 

Saprophagous,  373 

Sarcolemma,  *78 

Sarcophaga,  nervous  system  of,  *82 

Sarcophagous,  373 

Satiirma,  hairs  of,  *68 

Saunders,  429,  476 

Saville-Kent,  472 

Scales,  arrangement  of,  *7o;  development, 
70,  *7i;  form,  *6g,  *7i;  occurrence  of, 
69;  uses,  70 

Scape,  *32 

Scarabaeidoid  larva,  157 

Scavenger  insects,  236 

Schaffer,  on  scales,  70;  435,  441,  448 

Schenk,  on  sensilla,  84,  *85,  89,  445 

Schepotiefif,  6,  434 

Scheuring,  445 

Schewiakoff,  442 

Schiemenz,  446 

Schimper,  462 
32 


Schindler,  446 

Schistocerca,  distribution  of,  323,  339;  of 
Galapagos  Islands,  326;  isolation,  328 

Sckizoneura,  wax  of,  75 

Schizura,  protective  resemblance  of,  *io6 

Schmidt,  O.,  454 

Schmidt,  P.,  433,  448 

Schmidt-Schwedt,  449 

Schneider,  A.,  450 

Schneider,  R.,  440 

Schoene,  424 

Schon,  445 

Schroder,  436 

Schwarz,  on  distribution,  336,  337;  myrme- 
cophilism,  300,  471 

Schwedt,  455 

Sclerite,  28 

Scolopendra,  *5,  401 

Scolopendrella,  *6,  21 

Scorpion,  *2,  401 

Scudder,  on  albinism,  180;  coloration,  187; 
fossil  insects,  341,  345,  346,  347;  glaci- 
ation,  326;  mimicry,  203;  Orthoptera 
of  Galapagos  Islands,  326,  328;  spread 
of  P.  rapa,  338;  stridulation,  92;  443, 
457,  471,  473>  474 

Scutellum,  *45 

Scutum,  *45 

Seasonal  coloration,  180 

Sedgwick,  433 

Segmentation,  of  arthropods,  27;  germ 
band,  *i3i,  132;  head,  *43 

Segments  of  abdomen,  60 

Seitz,  457,  462,  466,  468,  471 

Sematic  colors,  210 

Seminal  ducts,  124;  receptacle,  125,  *i26; 
vesicle,  *i24 

Semon,  472 

Semper,  C,  on  scales,  70 

Semper,  K.,  471 

Sempers,  477 

Sense  organs,  83 

Sensilla,  84,  *8s 

Serosa,  *i3i,  *i34 

Sessili ventres,  *i9 

Setaceous,  *32 

Setae,  modifications  of,  69 

Seventeen-year  locust,  145 

Severin,  359,  371,  470 

Sex-determination,  376 

Sexual  coloration,  184 

Shannon,  472 


498 


INDEX 


Sharp,  on  AUa,  293;  Hawaiian  beetles,  326; 
metamorphosis,  159;  415,  431,  433,  449, 

455 

Sheath,  *64 

Shelford,  R.,  460 

Shelf ord,  V.  E.,  on  chemical  conditions,  383; 
communities,  393,  397;  environments, 
388,  389;  evaporation,  368,  369,  370, 
371;  physical  conditions,  384;  succes- 
sion, 404,  406,  407,  408;  tension  lines, 
399;  tiger  beetles,  174,  175,  183,  189, 
350;  459,  472,  474,  475,  576 

Sherman,  F.,  Jr.,  426 

Sherman,  J.  D.,  Jr.,  386,  456 

Shreve,  389,  391,  476 

ShuU,  94,  445 

Silk,  76 

Silk  glands,  75,  *y6 

Silkworm  (see  Bombyx  mori). 

Silpha,  distribution  of,  336 

Silurian  insects,  341 

Silvestri,  on  Anajapyx,  *6;  433,  434 

Simmermacher,  440 

Simpson,  358 

Simulium,  233;  respiration,  170 

Sinclair,  433 

Siphonaptera,  *2o;  origin  of,  *25,  26 

Sirex,  ovipositor  of,  *64 

Sirrine,  424 

Sitaris,  156 

Size  of  insects,  27 

Skin,  66 

SkuU,  28,  *29 

Skunk,  insectivorous,  236 

Sladen,  287,  467 

Sleep  of  insects,  352 

Sleight,  385,  456 

Slingerland,  411,  424,  477 

Smell,  87;  end-organs  of,  *88,  *89 

Sminthurus,  *io 

Smith,  E.  F.,  219 

Smith,  J.  B.,  425,  477 

Smith,  R.  C,  426 

Smith,  T.,  269 

Snodgrass,  24,  326,  328,  436,  438 

Snow  flea,  *io 

Snyder,  468 

Societies,  389 

Soil,  348;  nutriment  in,  351;  structure  of, 
348;  temperature,  350 

Soldier,  ants,  289;  termites,  *277 

Somatic  cells,  129 


Sorensen,  433 

Sounds,  91 

Spence,  431,  432 

Spermatheca,  125,  *i26 

Spermatogenesis,  129 

Spermatophores,  124 

Spermatozoa,  124,  *i25 

Sperm-nucleus,  129 

Speyer,  on  hermaphroditism,  126 

Sphecina,  277 

Sphecius,  277 

Sphex,  *223;  behavior  of,  316,  318,  *3i9 

Sphingidae,  as  poUenizers,  221,  *2  25 

Sphinx,  alimentary  tract  of,  *io4;  dispersal, 
323;  pulsations  of  heart,  112;  trans- 
formation, *i63 

Spichardt,  450 

Spillman,  268 

Spines,  69 

Spinneret,  *74,  75 

Spiracles,  closure  of,  *i2o;  number,  60,  119 

Sbiroholiis,  *3 

Si^irochata,  267 

Spongioplasm,  78 

Sporotrichum,  218,  367 

Spuler,  on  scales,  70;  438,  441,  458 

Spur,  *49 

Squama,  54 

Squash  bug,  metamorphosis  of,  *i38 

Stadium,  140 

Stagmomantis ,  leg  of,  *5o 

Standfuss,  temperature  experiments  of,  183, 
458 

Stedman,  426 

Stefanowska,  on  pigment,  99;  444 

Stegomyia,  255 

Stellwaag,  438 

Stenanima,  292 

Stenobothrus,  blood  corpuscles  of,  *iio; 
stridulation  of,  92 

Stenodictya,  *343,  344 

Stephens,  465 

Stereotropism,  303 

Sternberg,  250,  251,  464 

Sternum,  *47 

Stigmata  (,see  Spiracles). 

Sting  of  honey  bee,  *64 

Stinging  hairs,  *73 

Stings,  efficiency  of,  246 

Stipes,  *35,  37,  *38 

Stokes,  449 

Stomach,  *io4 


499 


Stomachic  ganglion,  8i,  *8s 

Stomatogastric  nerve,  8i,  *83 

Stomodaeum,  *io2,  131 

Strata,  393 

Slratiomys,  360 

Straton,  462 

Straus-Diirckheim,  on  muscles,  78;  435,  441 

Strength,  muscular,  79 

Strepsiptera,  17,  137,  157 

Stridulation,  92,  *93 

Strindberg,  453 

Strong,  R.  P.,  266 

Strottgylonotus,  294 

Structural  colors,  172 

Styloconicum,  84,  *85 

Stylops,  hypermetamorphosis  of,  157 

Subcosta,  *54 

Subgalea,  *38 

Submentum,  *35,  *38 

Suboesophageal  ganglion,  *8i,  *82 

Succession,  404;  causes  of,  404;  ecological, 
406;  of  forest  communities,  406;  geolog- 
ical, 404;  of  Orthoptera,  408;  seasonal, 
405;  of  tiger  beetles,  407 

Suctorial  mouth  parts,  38 

Suffusion,  178 

Summers,  426 

Superlingua;,  36,  *38,  *i32,  133 

Superlingual,  neuromere,  *43,  81,  135;  seg- 
ment, 44 

Supracesophageal  ganglion,  80,  *82 

Suranal  plate,  62,  *67 

Surface  film,  168 

Suspensor,  125 

Suspensory  muscles,  *iio 

Swarming,  286 

Swenk,  426 

Symbiosis,  299 

Symons,  426 

Sympathetic  system,  *8i,  *83 

Symphyla,  3,  *6 

Synchronism,  of  fireflies,  116 

SjTiecology,  348 

Syrphidae,  silk  glands  of,  77 

Systole,  III 

Tabanidae,  233  • 

Tabanus,   nervous   system,    *82;   olfactory 

organ,  *89 
Tachardia,  75 
Tactile  hairs,  69,  84,  *8s 
Tanidia,  *i2  2 


Tarantula,  401 

Tarsus,  *48 

Taschenberg,  430 

Taste,  84;  end-organs  of,  *86,  *87,  *88 

Taxis,  302 

Tegmina,  53 

Tegulae,  46 

Telea  polyphemus,  cocoon  of,  148;  eclosion, 
152;  larval  growth,  144;  silk  glands,  75; 
spinning,  151 

Teleas,  158 

Telson,  60 

Temperature,  352;  acclimatization  to,  360; 
on  activity,  353;  on  coloration,  182;  on 
distribution,  362;  on  hibernation,  361; 
on  incubation,  358;  limits,  352;  on 
reproduction,  358;  of  soil,  350 

Temperature-constant,  355 

Tenebrio  molitor,  development,  359,  360; 
incubation,  359;  metabolism,  370 

Tenent  hairs,  *72 

Tension  lines,  399 

Tenthredinidae,  larval  legs  of,  51 

Tenthredopsis,  larva  of,  *i42 

Tentorium,  29,  *3o 

Terebrantia,  *i9 

Tergites,  *45,  *46 

Tergum,  45 

Termites,  American  species  of,  279;  archi- 
tecture, *28o;  classes  of,  *277;  "com- 
pass," *28o,-  food  of,  279;  mandibles, 
*36;  origin  of  castes,  279;  queen,  *278; 
ravages,  281 

Termitidae,  11 

Termitophilism,  281 

Tertnitoxinia,  126,  127 

Termopsis,  278 

Tertiary  insects,  341,  345 

Testes,  *i24 

Tetralonia,  225 

Tettigoniidae,  10;  ovipositor,  *6y,  spermato- 
zoon, *I25 

Texas  fever,  269 

Thalessa  (see  Megarhyssa) . 

Thanaos,  androconia  of,  72;  claspers,  65 

Thayer,  461 

Thaxter,  on  Empusa,  217,  *2i8;  462 

Thelen,  449 

Theobald,  477 

Thermotropism,  312 

Thigmotropism,  303 

Thimm,  465  , 


500 


INDEX 


Thomas,  424,  427 

Thompson,  C.  B.,  443,  468 

Thompson,  S.  M.,  463 

Thorax,  differentiation  of,  44;  parts  of,  *45; 
sclerites  of,  *45,  *46,  *47 

Thread-press,  *76 

Thyridopteryx,  eggs  of,  141 

Thysanoptera,  *i4,  15;  origin  of,  22,,  *2$ 

Thysanura,  8,  *9;  abdominal  segments,  60; 
primitive,  20 

Thysanuriform,  24,  *i42,  *i43,  160 

Tibia,  48,  *49 

Tiger  beetles  (see  CicindelidcB) . 

Tillyard,  438,  476 

Tipula,  *2o 

Titanophasma,  27 

Toad,  insectivorous,  236 

Tongue,  37 

Torre-Bueno,  475 

Touch,  84 

Tower,  D.  G.,  437 

Tower,  W.  L.,  on  color  patterns,  186; 
cuticular  colors,  175;  distribution  of 
Lcptinoiarsa,  336;  folding  of  wing,  56, 
*57;  hibernation,  365;  integument, 
*67;  origin  of  wings,  53;  structural 
colors,  173;  441,  459,  472 

Townsend,  A.  B.,  448 

Townsend,  C.  H.  T.,  426 

Toxoptera  graminum,  development  of,  356, 
364;  distribution  of,  368 

Toyama,  451 

Tracheae,  development  of,  135,  *i36;  dis- 
tribution, *ii7,  *ii8;  structure,  *i2i 

Tracheal  gills,  *ii8,  169 

Tracheation,  types  of,  117 

Tracheoles,  *i2i,  122 

Trelease,  462 

Tremex,  *i9 

Trench  fever,  268 

Triassic  insects,  345 

Trie  kins,  225 

Trichodeum,  84,  *85 

Trichogen,  *68,  69,  *7i 

Trichogranima,  274 

Trichoptera,  18,  *i7;  origin  of,  *25;  silk 
glands,  77 

Trichopterygidae,  size  of,  27;  273 

Trimen,  on  dispersal,  323;  on  P.  ccnca,  202, 
205;  459,  460 

Trimerotropis,  protective  resemblance  of, 
196,  *i97 


Trimorphism,  180 

Triphleps,  egg  ofj  *i39 

Tritocerebrum,  80,  135 

Triungulin,  156,  *i57 

Trochanter,  48,  *49,  50 

Trochantin,  48 

Trogoderma,  2,11 

Tropcca  luna,  cocoon  of,  148 

Trophallaxis,  301 

Tropical  region,  335 

Tropidacris,  27;  respiratory  muscles  of,  *i23 

Tropisms,  302 

Trouessart,  471 

Trouvelot,  on  cocoon-spinning,   151;  eclo- 

sion,  152;  larval  growth,  144;  453 
Trypanosomes,  261,  *262,  *264 
Trypanosomiases,  261,  263,  264 
Tryphana,  116 
Tsetse  fly,  262,  *263 
Tuberculosis,  269 
Turner,  loi,  445 
Tutt,  472 

Typhoid  fever,  257 
Typhus,  266 

Uhler,  on  distribution,  337 

Uichanco,  358 

Underbill,  464 

Urech,  457,  458 

Uric  acid,  108;  as  a  pigment,  175 

Urosternite,  60 

Urotergite,  60 

Useful  insects,  411 

Utricularia,  217 

Uzel,  453 

Vagina,  125,  *i26 

Valette  St.  George,  la,  450 

Vanessa,  development  of  scales  of,  *7i ;  head 
of  butterfly,  *4o;  antiopa:  246;  photo- 
tropism,  309;  atalanla:  color  change, 
190;  cardui:  dispersion,  322,  326;  geo- 
graphical variation,  328;  polychloros: 
coloration,  179;  melanism,  180;  urticce: 
coloration,  176;  melanism,  180;  tem- 
perature experiments,  183 

Variation  in  coloration,  188,  *i9i,  *I92 

Variations,  190 

Vas  deferens,  *i24 

Vayssiere,  447,  449,  455 

Vedalia  (see  Novius). 

Vegetation  map  of  U.  S.,  *39i 


INDEX 


Veins,  *54 

Velum,  *228 

Venation,  *54 

Ventral  sinus,  no,  *i23 

Ventral  tube,  62 

Ventriculus,  *io4 

Verhoeff,  438,  439,  440,  466 

Vernon,  459 

Vertex,  28 

Vervvorn,  on  phototropism,  308;  469 

Vespa,  nests  of,  *288;  olfactory  organ,  *89; 

sensillum,  *85;  taste  cups,  *87;  tongue, 

*86 
Vespidas,  287 
Vestal,  394,  475 
Viallanes,  435,  442,  448,  454 
Vinal,  450 
Vision,  95 

Vitelline  membrane,  *i29 
Vitreous  body,  95,  *96 
Voliicclla,  mimicry  by,  *2io;  predaceous,  271 
Voss,  F.,  438 
Voss,  H.  v.,  459 

Wagner,  F.  v.,  459 

Wagner,  J.,  433 

Wagner,  N.,  450 

Wahl,  455 

Walker,  E.  M.,  434,  435 

Walker,  J.  J.,  456 

Walking,  51 

Walking-stick,  *i95 

Wallace,  on  mimicry,  203;  459,  460,  471 

Walsh,  on  losses  through  insects,  410;  424 

Walter,  on  mouth  parts,  40;  436 

Walton,  428 

Warming,  474 

Warning  coloration,  199 

Washburn,  425,  464 

Wasmann,  on  myrmecophilism,  297;  466, 
469,  470 

Wasps,  287 

Wasteneys,  470 

Watase,  444 

Water,  382;  circulation  of,  384;  contents 
of,  383;  depth,  386;  pressure,  385;  of 
soil,  350;  temperature  of,  385;  vegeta- 
tion of,  386 

Watson,  474 

Wax,  413 

Wax,  glands,  74;  pincers,  *2 28,^229 

Webb,  429 


Webster,  F.  M.,  on  dispersal,  323,  335,  338, 

368;  losses   through  insects,   410;  425, 

460,  462,  466,  471,  472 
Webster,  R.  L.,  426 
Wedde,  436 
Weed,  C.  M.,  on  birds  in  relation  to  insects, 

242,  243,  245;  426,  464 
Weinland,  444 
Weismann,  on  imaginal  buds,  161;  instinct, 

317;    temperature    experiments,    182; 

451,  453,  457,  458,  459,  460,  469 
Weiss,  156,  311,  475 
Welch,  456 
Welles,  447 
Wesche,  437 

West  wood,  on  Brachinus,  73;  431,  432 
Wheeler,  on  ants,  289,  297,  320;  Malpighian 

tubes,  108;  protective  coloration,  178; 

trophallaxis,  301;  tropisms,  302,  303, 

305,  306,  311;  439,  447,  448,  452,  453, 

467,  468,  469 
White,  F.  B.,  455 
Whitman,  469 

Whymper,  on  distribution,  322;  472 
Wickham,  347 
Wielowiejski,  von,  448,  450 
Wilcox,  451,  463 
Wilde,  446 
Wilder,  267 

Will,  F.,  on  taste,  85;  444 
Will,  L.,  450,  452 
Williams,  C.  B.,  434 
Williams,  T.,  449,  455 
Wilson,  453 
Wilt,  cucurbit,  219 
Wind,  distribution  by,  323,  368 
Wings,  53;  folding  of,  56,  *57;  modifications 

of,  53;  muscles  of,  *59;  venation,   *54; 

vibration,  57,  *58,  91 
Wistinghausen,  von,  449 
Witlaczil,  440,  447,  452,  454 
W^odsedalek,  377 
Wollaston,  on  beetles  of  Madeira  Islands, 

326 
Woodward,  453  ' 

Woodworth,  425,  438 
Worker,  ant,  289;  bee,  *282,  286;  termite, 
277,  *278;  wasp,  288 

Xanthophyll,  as  a  pigment,  176,  193 
Xenoneura,  *342 
Xiphidium,  stridulation  of,  92 


502 


INDEX 


Yapp,  369  Z  ait  ha,  171 

Yaws,  269  Zander,  440 

Yellow  fever,  252  Zeuzera  pyrina,  419 

Yolk,  *i29,  *i3o  Zittel,  von,  433 

Yothers,  361,  377  Zones,  life,  *2,3z 

Young,  R.  T.,  461  Zoraptera,  12,  22 

Yuasa,  437  Zorotypus,  12,  22 

Yucca,  pollination  of,  222,  *2  24  Zugmayer,  461 


a: 


I 


